103-2 ?TMFNT of flf'FAN(1f;RAPNY
NENAL EM R.
rILLAMOOK BAY'
SCHOOL of SCIENCE
OREGON STATE UNIVERSITY
FINAL REPORT:
SPECIES COMPOSITION
AND DISTRIBUTION OF
MARINE NEKTON IN THE
PACIFIC OCEAN
OFF OREGON
ATOMIC ENERGY COMMISSION
CONTRACT AT(45-1)1726
Reference 63-26
September 1961-1963
L
September 1963
SPECIES COMPOSITION AND DISTRIBUTION OF MARINE NEKTON IN THE
PACIFIC OCEAN OFF OREGON
Final Progress Report
1 September 1961 through l September 1963
Atomic Energy Commission
Contract AT(45-1)1726
Department of Oceanography
Oregon State University
m"
FINAL REPORT:
SPECIES COMPOSITION OF MARINE NEKTON IN THE PACIFIC OCEAN
OFF OREGON
CONTENTS
Page
Summary ............................................................
Distribution and Ecology
Section
1.
Section
2.
Preliminary Observations on the Distribution of
Mesopelagic Fishes off Oregon ..........................
13
Species Composition and Distribution of Pelagic
Cephalopods From the Pacific Ocean off Oregon,
1961-1963 ..............................................
Section
3.
Section
4.
Notes on the Occurrence and Distribution of
Macroplankton off the Oregon Coast .....................
37
49
Vertical Distribution of the Numbers and Biomass of
Mesopelagic Fishes with an Improved Isaacs-Kidd
Midwater Trawl ..........................................
67
Radioecology
Section
5.
Notes on the Vertical Distribution of Zinc-65
Zirconium-95 from Oceanic
Section
6.
Section 7.
and
Animals ......................
Radioactivity and its Relationship to Oceanic Food
Chains .................................................
Zinc-65 in Euphausiids as Related to Columbia River
Water off Oregon .......................................
81
91
107
Publications and Papers ............................................ 131
LIST OF FIGURES
Follows
page
Figs.
Section 1.
1.
Location of midwater trawling stations off Oregon..........
14
2.
Catches of the four dominant mesopelagic fishes in the
upper 200 m ................................................
16
The variability of catches of the four dominant mesopelagic fishes .............................................
18
Depth variations in the catches of three lantern fishes
at night .................................................
20
A temperature and salinity profile, 50 miles off Newport,
Oregon, August 1961 ........................................
22
6a.
Average monthly catches of Lampanyctus leucopsarus .........
26
6b.
Average monthly catches of Diaphus theta ...................
26
3.
4.
5.
Section 2.
Location of midwater trawling stations off the Oregon
coast ......................................................
38
The relative abundance of pelagic cephalopods found off
Oregon in midwater trawl samples ...........................
40
3.
Size-frequency distribution of Abraliopsis .................
46
4.
Size-frequency distribution of Gonatus fabricii and Gonatus
Larvae .....................................................
46
1.
2.
Section 3.
1.
The distribution of adult and larval forms of similis for
June, July, and August 1961 ................................
as recorded
58
2.
Salp catch
by the midwater trawl (1961-1963)...
60
3.
Catches of two chaetognaths during January 1962 at three
latitudes off Oregon .......................................
64
Follows
Section 4.
Isaacs-Kidd midwater trawl showing the depth-distance recorder
mounted on the depth depressor ................................
70
Duplication of a trace made with the depth-distance recorder
on a tow which sampled three depths within the upper 1000 m...
70
3.
Histograms showing the number of fishes captured per 1000 m3
76
4.
Histograms showing the wet weight of fishes collected per
1000 m3....
.................................................
76
1.
2.
Section 5.
1.
Zn65 and Zr95-Nb95 contents in pelagic animals for day and
night periods .................................................
86
Section 6.
1.
Comparison of gamma emitters from several trophic levels ......
96
2.
Concentrations of gamma emitters from several trophic levels..
98
3.
Comparison of spectra of euphausiids and copepods from the
same sample ...................................................
100
Comparison of spectra of euphausiids and sergestids from the
same sample .................... ..............................
100
4.
Section 7.
1.
Gamma-ray spectra of particulate material in two Oregon rivers
112
2.
Zinc-65 in euphausiids and salinity distribution during
summer 1961 ...................
112
3.
Same as Figure 2 for November 1961 ............................
112
4.
Same as Figure 2 for January 1962 .............................
112
5.
Same as Figure 2 for March-April 1962 .........................
114
6.
Same as Figure 2 for July-August 1962 .........................
114
FINAL REPORT:
SPECIES COMPOSITION OF MARINE NEKTON IN THE PACIFIC OCEAN
OFF OREGON
SUMMARY
This report summarizes the results of the research contract,
"Species Composition and Distribution
of Marine
Nekton in the Pacific
Ocean off Oregon" (AT(45-1)1726) for the two-year period from September
1, 1961, to September 1, 1963.
INTRODUCTION
Since it has been found that animals can accumulate and concentrate
radioisotopes from their environment, their role in the biological transport of nuclides in the ocean has become of great interest.
Nektonic or
swimming animals (fishes, squids, shrimps, euphausiids, etc.) are known
to undertake extensive vertical migrations, often through density
gradients of the thermocline or halocline and into surface waters, and
the movements of these pelagic animals may be more important than simple
physical processes in the transport and distribution of radioisotopes in
the ocean.
Lateral movements of these animals may also be important in
determining the fate of radionuclides introduced into the sea.
However,
virtually nothing is known about the extent of lateral movements of small,
oceanic nekton.
These animals are basic forage for higher consumers
such as salmon and albacore.
It is apparent, therefore, that there is a
need to broaden our understanding of the ecology, distribution, and move-
ments of these ubiquitous swimming animals that are intermediate in the
oceanic food chain.
Study of the oceanic nekton off Oregon was of interest for several
reasons.
First, no detailed studies of the
oceanic fauna in this region
2
of the northeastern Pacific Ocean had ever been made. Little was known,
therefore, about the
species composition
Secondly, the Pacific
or distribution
of marine nekton.
Ocean off Oregon and Washington, because of the
presence of the Columbia River, provides an exceptional opportunity for
cooperative ecological
from Hanford
reactors
both biologically
This provides
and radiological
research.
on this river maintains
Neutron activation
a "steady
state"
source of
important and biologically inert isotopes in the ocean.
a unique natural situation
for a radioecological study,
the results of which have applicability to the accidental or intentional
disposal of radioactive materials
at sea.
Information on species of
animals and their distribution is a prerequisite for interpretation of
radioecological data.
SAMPLING PROGRAM
In order to provide data on the distribution of oceanic nekton,
and
more specifically, on spatial and temporal variations in distribution
and species composition, a systematic sampling program was established
in which standard collections were made routinely at predesignated sta-
tions from 15 to 165 miles offshore along three latitudes off Oregon
during every season of the year.
This intensive sampling program was
designed so that the distribution of animals could be compared between
(1) stations across the continental slope, (2) latitudes, and (3) seasons
of the year.
In addition, collections at successive depths down to 1000
m were made routinely at a station over the outer continental slope, providing data on depth distribution and vertical migration.
During the
3
two-year period of the contract, 44 cruises of the R/V ACONA were made in
support of this program.
A total of 353 samples with an Isaacs-Kidd
For
midwater trawl and 38 samples with a meter plankton net were taken.
details on sampling and methods, see Section I.
OBJECTIVES
The primary objectives on the contract as stated in the original
proposal and renewal request were as follows:
(A) Characterization of the species composition of oceanic marine
nekton and macroplankton off Oregon.
(B) Distribution of animals, specifically spatio-temporal differences
related to (1) depth and diurnal vertical migration,, (2) distance from
shore,
(3) latitude, and (4) seasons of the year.
(C) Collections and identification of oceanic animals for radioanalyses and assisting in the interpretation of resulting data.
SUMMARY OF RESULTS
This section outlines the realization of the objectives stated
above.
A. Species Composition
The major groups of oceanic marine nekton and macroplankton were
studied taxonomically.
The results represent the first detailed study
of the species composition of these animals off the Oregon coast.
Such
data are basic to further research on radioecology or distributional
analyses.
4
Taxonomic data for the collected material are summarized in the respective results sections:
FISHES
(Section 1)
CEPHALOPODS
(Section 2, Reprint 2)
MACROPLANKTON
EUPHAUSIIDS
(Section 3A)
NATANT SHRIMPS
(Section 3B)
SALPS
(Section 3C)
MEDUSAE, SIPHONOPHORES,
(Section 3D)
and CHAETOGNATHS
A new species of squid and peculiar gelatinous egg masses of fish
were described from the collected material (Reprint 1 and 2).
B. Distribution of Nektonic Animals
Study of variations in the distribution or abundance of oceanic
animals has several inherent difficulties.
The very nature of the open
ocean environment imposes limitations on any sampling program.
Numerous
and repeated samples, desirable from a statistical standpoint, are made
impractical due to the expense of ship operations.
Patchy distribution
of many marine organisms also leads to large variances, resulting in
statistical analyses which suffer from insensitivity.
Furthermore,
available sampling devices for nektonic animals are at best only semiquantitative.
These sampling problems were anticipated (see original
proposal), and some attempt was made to measure the degree of variability
encountered during repeated tows.
For instance, coefficients of variation
calculated for the catches of certain common fishes collected during one
night at one station revealed
a wide range
of variability; high coefficients
suggested patchy distribution or schooling activity (see Section 1).
Thus, reliable assessment of differences in distribution of such
oceanic populations, unless pronounced, require continued, long-term study.
Despite these difficulties, however, it was possible to characterize cer-
tain features of the distribution of nekton off Oregon.
Seasonal Occurrence and Variations
1. Species Composition
No marked seasonal variations were observed in the fundamental
species composition of mesopelagic fishes (Section 1) or oceanic cephalopods (Section 2) collected off Oregon during the study period.
The same
dominant species prevailed in the upper 200 m in most oceanic samples.
This is in
contrast
with
neritic areas or large nekton where distinct
seasonal changes may result from the migratory habits of many species.
Seasonal variations in the concentration of
Zn65
in euphausiids off Oregon
were much less than the seasonal variations observed in Columbia River
plume waters as determined by lowered salinities.
This too may be inter-
preted as evidence for a rather stable population of oceanic animals (see
Section 7),
2, Seasonal Differences in Relative Abundance
Although no marked seasonal changes in the species composition of
nekton were evident in the ocean off Oregon, seasonal
variations in the
catches of common species of fishes and squids were noted.
In both cases,
highest catches were made during summer months, especially at stations
6
over the inner continental slope.
The seasonal differences for the two
dominant species of mesopelagic fishes (Lampanyctus leucopsarus and Diaphus
theta) were generally significant statistically (see Section 1).
The two
dominant species of oceanic squids (Gonatus fabricii and Abraliopsis sp.)
were six to eight times more common in collections during the summer than
other seasons of the year (Section 2).
In some cases these seasonal dif-
ferences may be caused by increased availability of animals due to currents.
In the case of Abraliopsis, however, the increased catches in the summer
were accounted for by large numbers of young animals.
This was also the
case with the shrimp, Sergestes similis (Section 3B).
Consequently,
these seasonal maxima could be explained by seasonal breeding and recruitment.
This indicates the importance of analyzing the size-structure of
the populations at different seasons.
The study of seasonal variations
provided some interesting indications, but no general conclusions can be
drawn on the consistency of these trends due to the limited data.
Geographic Distribution and Variations
1, Latitudinal Distribution
In general, little difference was apparent in the species composition
or structure among the various east-west lines of stations,
In the fishes,
as with the euphausiids and salps, there were indications that the species
diversity increased to the south, but there was no evidence for large
latitudinal movements (See Section 1, 3A, and 3C).
Variations in the relative abundance of certain nekton associated
with distance from shore were suggested from the catch statistics.
Highest
catches of fishes and cephalopods were made at nearshore oceanic stations
7
during the summer months, whereas, during other seasons catches along the
station lines were more uniform (Section 1, Fig. 6).
Another rather con-
sistent feature was the notable lack of oceanic nekton at the shallow
water stations off Newport (Section 1).
Since this was apparent during
the current patterns of various seasons, it suggests that these animals
are able to influence their own geographic position and remain in deep
water by laterial movements.
Depth Distribution and Vertical Migration
1. Day-Night Differences Within the Upper 200 m
Distinct differences in the number of mesopelagic animals during
day and night periods within the upper 200 m were found.
For example,
few mesopelagic fishes were taken during daylight hours within these
Differences in the upper
upper waters, but they were abundant at night.
depth ranges of the dominant lantern fishes were noted by trawling to
successive depths within the upper 100 m.
From these data, it was con-
cluded that the four common species of fishes migrate vertically through
the density gradients of the halocline; moreover, some species cross the
thermocline as well (for details, see Section 1).
2. Vertical Distribution Within the Upper 1000 m
Comparison of successive tows to 200,
500,
and 1000 m depths indi-
cated that some species of oceanic nekton do not commonly migrate into
epipelagic waters at night (Section 1, 2, 3A, and
study is required
to learn the
3B).
However, more
extent, if any, of migrations below 500 m.
8
Adaptation of the Lamont Multiple Plankton Sampler (MPS) as an openingclosing cod-end collecting unit for the midwater trawl, along with other
modifications of the trawl, provided quantitative data on the depth distribution of oceanic animals.
Section 4 summarizes these results giving
first estimates for the vertical distribution of mesopelagic fishes.
This
study indicated that.
(1) Most of the collected biomass occurred within the upper 500 m;
average biomass between 500 and 1000 m was comparatively low on a gramper-cubic-meter basis,
(2) During the day, highest catch number (g/m3) usually occurred at
mid-depths (200-500 m), whereas, during the night, there was a large
increase in the number and biomass collected in the upper 200 m.
These
differences are evidence that a large portion of the biomass is involved
in vertical migration from mid-depths into upper waters.
There was no
apparent difference in the day and night biomass collected below 500 m.
(3) A higher biomass per square meter of surface (down to 1000 m)
collected at night appeared to be due to the larger average size of fish
captured in the night collections.
C. Radioecology of Oceanic Animals
Studies of the radioecology of oceanic animals off Oregon were the
joint
result
responsible
of AT(45-1)1726 and AT(45-1)1750.
for the
The former contract was
collection of samples necessary for radioanalyses.
As a result of this cooperative
effort,
a large number of
macroplankton (euphausiids, salps, shrimps, copepods)
and fishes)
Reprints
animals,
including
and nekton (squids,
have been studied by gamma-ray spectrometry (Sections 6 & 7;
4, 5, and 6),
9
A
Some of the results of these studies are included in this report.
preliminary study of the vertical distribution of Zn65 and Zr95-Nb95 from
oceanic animals collected at different depths is found in Section 5.
This
section indicates that the amount of Zr95-Nb95 in the animals collected
decreased rapidly with depth,
The Zn65 content, on the other hand, was
nearly the same in animals from all depths within the upper 1000 m,
Calculation of the amount of Zn65 in the animals per 1000 m3 of water
filtered illustrated a definite flux of radiozinc into surface waters
during the night,
This movement indicates the importance of the vertical
migration of animals in affecting the distribution of this radionuclide
off Oregon,
Comparison of the gamma-ray spectra from various levels of the
oceanic food chain (Section 6) revealed that fission products, such as
Zr95-Nb95 and
were concentrated only by herbivores and were dis-
criminated against by the carnivores,
This conclusion is further supported
by the fact that the Zr95-Nb95 content of deep water animals, which are
mainly predators, was also low (Section-5).
Seasonal and geographic variations in the.Zn65 content of Euphausia
pacifica are discussed in.Section 7.
Noteworthy is the conclusion that
in spite of seasonal differencesinthe position'of the Columbia River
plume, the radiozinc concentration in euphausiids remained fairly constant throughout the year.
uncertain.
Th
reasons for this stability are at present
Diurnal migration of euphausiids, seasonal changes of currents,
and a long biological half-life of Zn65
causes.
are suggested as
contributory
PRELIMINARY OBSERVATIONS ON THE DISTRIBUTION
OF MESOPELAGIC FISHES OFF OREGON
by
William
G.
Pearcy
ABSTRACT
Over 200 collections made throughout the year with a midwater trawl
to various depths down to 1000 m and along three latitudes off Oregon
provided preliminary data on species composition, sampling variability,
daily vertical migrations, depth distribution, and seasonal and geographic variations of mesopelagic fishes.
About 40 species of mesopelagic fishes were collected.
Half the
number of species were present in 0-200 m collections, half in deeper
collections.
Those frequently occurring only in collections to 500 or
1000 m are listed as lower mesopelagic fishes.
Those found above 200 m
at night, or upper mesopelagic fishes, dominated most collections.
were largely the lantern fishes.
These
Differences in upper depth distributions
of the dominant lantern fishes were evident at night; all penetrated the
halocline, and some crossed the density gradient of the thermocline as well.
Although no clear seasonal changes in species composition were apparent
high catches of dominant fishes during the summer and low catches during
other seasons suggested seasonal changes in relative abundance, perhaps
due to movements across the continental slope.
Mesopelagic fishes were
common over the continental slope but were rare over the shelf,
that depth limits their horizontal distribution.
The diversity
indicating
of meso-
pelagic fishes, as well as the catches of several species, increased from
north to south,
12
INTRODUCTION
Knowledge of the ecology of animals of the open oceans is very
limited.
This is particularly true of the small nektonic organisms, such,
as fish, squid, and shrimp that are intermediate in the food web between
small plankton and larger carnivores.
ubiquitous in the oceans of the world.
These micronektonic animals are
As nekton, they are capable of
sustained movements, independent of currents, in horizontal or vertical
directions.
The occurrence of vertical migrations of micronekton has been well
documented since the CHALLENGER Expedition (Brauer, 1906; Murray and
Hjort, 1912; Beebe and Vander Pyl, 1944; Tucker, 1951; Bainbridge, 1961;
and others).
Horizontal movements, on the other hand, although described
for many of the larger epipelagic nekton, have not been adequately
studied for the smaller mesopelagic nekton.
Mesopelagic animals are de-
fined as those distributed between 200 m and 1000 m depth during the day.
(For classifications of epipelagic, mesopelagic and.bathypelagic zones,
see Hedgpeth (1957).)
The studies of mesopelagic fishes by Taning (1918).
Barham (1956), and Fast (1960), revealed seasonal differences in the
catches of certain species of lantern fishes that suggested' horizontal
movements of these populations.
Whether such movements are of a general
nature for mesopelagic animals, how these movements are affected, how far
they extend, and how they are related to the ecology of the populations
are questions of real interest to the biological oceanographer.
A purpose of this study on the distribution of midwater fishes off
Oregon is to examine possible changes in the catches of mesopelagic fishes
which may reflect seasonal movements across the continental slope, that
13
transitional area of the oceanic region
the neritic
bility,
region is
gross features
approached.
where depth
decreases rapidly as
Species composition, sampling varia-
of depth distribution and vertical
migrations are
also discussed.
Aron (1959, 1962) conducted extensive midwater trawling studies in
the eastern North Pacific and contributed much to our knowledge of the
zoogeography of oceanic animals.
His collections extended over a wide
geographic area but were limited to shallower depths and the summer and
fall seasons.
The present study entails systematic sampling of a rela-
tively small area of the Pacific Ocean to greater depths on a year-round
basis; it represents the largest number of collections to depths below
500 m and during the winter
season for
this
area of the Pacific.
No
previous studies have surveyed this area.
In view of their swimming capacity, nektonic animals may be important
agents in the distribution and transport of radioisotopes.
Detectable
quantities of radioisotopes, such as zinc-65 induced in low levels by
the Hanford nuclear reactors on the Columbia River, have been found in
micronekton such as lantern fishes, sergestid prawns, and euphausiids off
Oregon (Osterberg, 1962; Osterberg, et al., in press).
These micronekton
are capable of crossing density. gradients such as the thermocline and
halocline, which normally inhibit mixing by physical processes.
migrations of these animals may make them available
as forage
Inshore
for commer-
cially important species, which in turn may make these radioelements
available to humans.
If the open oceans are used for disposal of radio-
active materials, obviously a more comprehensive understanding of nekton
ecology and behavior is essential (Ketchum, 1960).
14
METHODS
Micronekton were sampled with a six-foot Isaacs-Kidd midwater trawl
(Isaacs and Kidd, 1953; Aron, 1962),
A total of 228 collections were made
on cruises between June 1961 and August 1962.
Collections were made
during various seasons of the year at stations located 15, 25, 45, 65,
and between 85 and 165 miles offshore along three parallels of latitude
off (1) the mouth of the Columbia River (35 collections),
(2) Newport
(46 collections), and (3) Coos Bay (29 collections) (Fig. 1).
An oblique tow to 200 m depth was made at each station with the
midwater trawl.
The net was lowered rapidly until 730 m of wire were out
and then retrieved at a constant speed of 30 meters per minute while
steaming on a given compass course at six knots,
Where the depth of the
bottom would not permit tows to 200 m, shallow tows were made with a
reduced rate of retrieval and an increased towing speed.
Thus, the speed
of the net through the water and the total time for the tow were approximately the same regardless of the depth of the water,
along the three east-west series were made at night.
All collections
Usually the inshore
stations (15-65 miles offshore) were sampled during one evening,
and.the
remaining station was sampled the following night.
One hundred eighteen tows were made at a station 50 miles off Newport
over the outer edge of the continental slope (encircled station in Fig. 1).
These tows included (1) repeated tows in the upper 200 m over periods
varying from 6 to 48 hours to evaluate sampling variability and daily
changes in relative abundance, and (2) successive tows to.various depths,
generally 200, 500, and 1000 m, to gain information on vertical distribution,
I
126°
124°
WASHINGTON
`
ASTORIA
OREGON
NEWPORT
CALIFORNIA
128°
Figure 1.
126°
124°
Location of midwater trawling stations off Oregon. Numbers
designate the distance in miles from the, coast. The circle
50 miles off Newport, Oregon, includes the location of replicate
tows and tows to various depths.
l"
The relationship between the maximum depth of the trawl and the length
of the towing wire was determined with either a bathythermograph or depth
gauge attached to the
The results, given
trawl.
below,
showed that a wire
length of approximately four times the desired depth was required.
maximum depth
m wire
desired depth
730
2000
4000
200 m
500 m
1000 m
No, obs.
39
3
3
.(average)
maximum depth
variation
Standard Deviation = 8.1
193
533
1007
430-600 (range)
960-1080 (range)
For tows to 500 m the trawl was fished between 500 and 200 m (2000-730 m-
wire) for about 30 minutes and for twos to 1000 m between 1000 and 500 m
(4000-2000 wire) for one hour.
Upon reaching the upper depth interval,
the trawl was retrieved at the rate of 50-70 meters of wire per minute.
All collections were made from the R/V ACONA.
Since the main winch
is located forward, the wire was secured in a towing block on the stern
to facilitate a constant heading while towing.
Geographic position at
the start and end of each tow, total duration of the tow, course, speed,
and sea and weather conditions were recorded for all collections.
Samples were preserved with formalin at sea.
Later, all fishes and
other nekton were sorted, identified and measured in the laboratory ashore.
SPECIES COMPOSITION
Over 40 species of fishes were identified from the collections
(Table 1).
Mesopelagic fishes dominated the catches in both number and
variety. Myctophidae, Melanostomiatidae, and Gonostomatidae were most
abundant.
Three species of Myctophidae, or lantern fishes, accounted for
76 percent of the total catch: Lampanyctus leucopsarus (45 percent),
16
Diaphus theta (21 percent) and Tarletonbeania crenularis (10 percent).
Both L. leucopsarus and D.,theta occurred in over 80 percent of all collections (excluding day tows within the upper 200 m and tows in neritic
waters).
Tactostoma-macropus, a melanostomiatid, composed approximately
8 percent of the total catch.
These fishes represented the four most
abundant species found in our collections.
Although numerically unimportant, epipelagic fishes were also collected,
Included were such oceanic species as the saury, Cololabis
saira, and neritic species as smelt, cod, etc.
However, relatively few
collections were made over the continental shelf, and fishes over the
slope, especially those migrating into the upper 200 m at night, were
sampled preferentially.
Although numerous larval fishes were collected,
they are not considered in this paper.
DAY-NIGHT VARIATION AND SAMPLING VARIABILITY
Variations in the numbers of the four dominant mesopelagic fishes
collected during night and day periods are illustrated in Figure 2.
The
positions of all these collections are encompassed by the circle in Figure
1,
Diurnal (diet) differences are obvious; catches of these fishes within
the upper 200 m were high during the night compared with the day,
While differences between day and night catches were clear, there
was no evident trand in the catches of fishes during the night that indicated major variations associated with time.
Since catches soon after
sunset or before sunrise were not consistently lower than those made
around midnight, it is believed that fish ascended quickly to the upper
200 m shortly after sunset and remained within this region until shortly
NIGHT
DAY
0400
HOUR
0800
1200
0000
2000
1600
0400
vffiz
13-14 July 1961
T. macropus
0
1
0
0
26
0
0
0
0
0
0
0
5
0
L. leucopsarue
0
T. crenularis
D, theta
3
2
0
5 14
5
1
0
0
0
0
10
2
3
1
1
1
0104
17-18 July 1961
T. macropue
L. leucopsarus
T. crenularis
D. theta
0
0
3
2
1
1
0
8
5
6
0
0
4 30
1
0
0
3
13
9
3
1
1
15 25
9
7
11
3
8
11
2
23-24 Jan, 1962
T. macropue
T.
D.
0
4
0
2
3
5
0
1
1
0
3
2
5
3
0
L. leucopsarus
crenularis
theta
0
24-25 Jan. 1962
T. macropus
0
0
0
0
L. leucopearua
T. crenularis
D, theta
1
2
2
0
0
10
10
7
9
7
1
2
3
1
8
6
3
2
1
2
1
1
9
6
8
8
2
0
15
2
4
4
9
2
3
7
4
7
5
5
1041 April 1962
T. macropus
0
L. leucopearus
0
5
2
0
0
2
9
0
0
0
0
2
1
2
T. crenularis
.D. theta
11-12 April 1962
T. macropue
L. leucopsarue
T. crenularis
D. theta
Figure 2.
1
9
3
10
7
12
4
9
2
7
5
9
2
6
2
0
2
1
1
1
0
2
1
1
4
3
2
2
2
1
2
5
2 10
10 10
Catches of the four dominant mesopelagic fishes in the upper
200 m 50 miles off Newport, Oregon.
17
Table I.
Fishes collected during midwater trawling
studies off Oregon
MES0PELAGIC
Bathylagidae
Bathylagus ochotensis Schmidt, 1938
B. milleri Jordan and Gilbert, 1898
B. pacificus Gilbert, 1890
Opisthoproctidae
Macropinna microstoma Chapman, 1939
Bathylychnops exilis Cohen, 1958
Alepocephalidae
Talismania bifurcata (Parr, 1951)
Searsidae
Holtbyrnia polycoeca (Parr, 1937)
Idiacanthidae
Idiacanthus antrostomus
Gilbert, 1890
Myctophidae
Ilierops crockeri (Bolin, 1939)
H. thompsoni (Chapman, 1944)
Myctophum californiense Eigenmann and Eigenmann, 1889
Tarletonbeania crenularis (Jordan and Gilbert, 1880)
Diaphus theta Eigenmann and Eigenmann, 1890
Lampanyctus nannochir (Gilbert, 1890)
L. leucopsarus (Eigenmann and Eigenmann, 1890)
L. ritteri Gilbert, 1915
L. regalia (Gilbert, 1891)
Ceratoscopelus townsendi (Eigenmann and Eigenmann, 1889)
Scopelarchidae
Neoscopelarchoides dentatus Chapman, 1939
Gonostomatidae
Cyclothone signata Garman, 1899
C. microdon (Gunther, 1878)
C. pallida Brauer, 1902
Paralepidae
C. acclinidens Garman, 1899
C. spp.
Danaphos oculatus (Garman, 1899)
Cetomimidae
Lestidium ringens (Jordan and Gilbert, 1881)
1 sp.
Sternoptychidae
Argyropelecus lynchus Garman, 1899
A. intermedius Clarke, 1877
A. pacificus Schultz, 1961
Melanostomiatidae
Bathophilus flemingi Aron and McCrery, 1958
Tactostoma macropus Bolin, 1939
Malacosteidae
Aristostomias scintillans (Gilbert, 1915)
Nemichthyidae
Nemichthys scolopaceus Richardson, 1848
Anoplogastridae
Anoplogaster cornuta (Valenciennes, 1833)
Melamphaidae
Poromitra crassiceps (Gunther, 1878)
Oneirodidae
2 spp.
Chauliodontidae
Chauliodus macouni Bean, 1890
NERITIC
-------
EPIPELAGIC
----------
Petromyzontidae
Entosphenus tridentatus (Gairdner, 1836)
A N D
O THE R S
Scorpaenidae
several spp.
Engraulidae
Engraulis mordax Girard, 1854
Cottidae
Scorpaenichthys marmoratus (Ayres, 1854)
Osmeridae
Agonidae
Agonopsis emmelane (Jordan and Starks, 1895)
Thaleichthys pacificus (Richardson, 1836)
Scomberesocidae
Cololabis saira (Brevoort, 1850)
Gad idae
Microgadus proximus (Girard, 1854)
Coryphaenoididae
1 sp.
Icosteidae
Icosteus aenigmaticus Lockington, 1880
Liparidae
Nectoliparis pelagicus Gilbert and Burke, 1910
Anarrhichadidae
Anarrhichthys
ocellatus Ayres, 1855
Zoaricdae
Lycodapus mandibularis Gilbert, 1915
18
before dawn.
Therefore, though fishes may have migrated vertically within
the upper 200 m region during the night, all tows during this period were
By
assumed to have sampled the same mesopelagic population of fishes.
assuming that these night tows represent replicate samples, a basis is
provided for estimates of sampling variability,
This is useful to eval-
uate subsequent spatial and temporal differences and to gain insight on
the patchiness of distribution of mesopelagic fishes,
Figure 3 shows the average catch of each of the four species plotted
against the respective variance (calculated from the data given in Figure
2, excluding series in which less than four night collections were made).
If the distribution were random (Poisson) the variance would be approximately equal to the mean, and points would be grouped near the 450
diagonal,
dispersion,
To estimate the departure from randomness, coefficients of
s?/x
(Blackman, 1942) were calculated, and the significance
of their deviation from unity compared to the expression
1
2
2n
(n-1)2
where n is the number of samples (Holme, 1950).
The large range of the
16 coefficients calculated for these four species (from 0,3 to 12,3)
indicates a lack of a consistent dispersion pattern.
Eleven coefficients
of dispersion did not significantly depart from unity and are clustered
near the 450 diagonal; although this suggests a random distribution,
these occur at low population densities where the sample size is probably
too small for reliable estimates of the actual distribution (Cassie,
1959),
Five coefficients were significantly greater than would be ex-
pected from a randomly distributed population,
These large values
99
115
5.7
A
CO
N
0
/
/
/
/
O
T. macropus
L. Ieucopsarus
L
T. crenularis
D. theta
T
5
10
15
20
-
-
25
MEAN (x)
Figure 3.
The variability of catches of the four dominant mesopelagic
fishes. The 45° dashed line denotes random (Poisson) distribution.
19
occurred when average catches were high, suggesting aggregation (over-dispersion)
at high densities for all four
species.
A noteworthy example of
such patchy distribution was the catch of 95 T. crenularis in one tow,
compared with
the usual 2 or 3 per collection,
Aggregation at high densities has been reported for many
including marine plankton (Barnes and Marshall,
natural
populations,
1951).
These indications of aggregations
distribution
of the
other,
may reflect the actual spatial
animals, but it is also
possible that inconsistencies
in sampling, such as failure to sample all depths equally, may lead to
such conclusions.
Since aggregation and high densities were both appa-
rent only from the summer catches, seasonal changes in spatial distribu-
tion, perhaps related to schooling or breeding activity, are suggested.
Although there is insufficient data on schooling and spatial distribution
of mesopelagic fishes, small schools of lantern fishes have actually been
observed from a bathysphere by Beebe (1934) or a bathyscaphe by Peres
(1958),
Variability of catches of certain myctophids off California was..
also attributed to their schooling behavior by Beebe and Vander Pyl (1944).
Aron (1962) reported that the difference in the total number of
fishes caught between repeated midwater collections was always less than
a factor of two. This suggests a more random distribution of fishes
and much less sampling variability than noted in our study above.
The
apparent disparity between the two studies may be because different areas
were sampled and different sampling techniques were used (Aron fished his
trawl at one depth for 30 minutes).
Also the total catch of fish may
vary less than the catch of individual species.
20
DEPTH DISTRIBUTION
Although opening-closing devices are necessary for a detailed analysis of depth distribution, some generalizations are possible from a study
of collections with non-closing nets to successive depths or during
periods of daylight and darkness,
Depth distribution of the catches of three different lantern fishes
(Fig, 4) illustrates the percentage of the total, number of a species
collected in tows to various depths,
Depths indicated are depths to
which tows were made and not necessarily depths at which fish were captured,
Despite these limitations, the data clearly demonstrate dif-
ferences in vertical distribution for different species.
For example,
most Tarletonbeania crenularis were collected at the surface and were
less abundant in tows below 10 m depth,
This species, incidentally, is
commonly collected with dip nets under night-lights off Oregon,
On the
other, hand, neither Diaphus theta nor Lampanyctus leucopsarus were cap-
tured at the surface but were found in highest numbers below 10 m; D.
theta was most abundant in tows to 10-25 m and L, leucopsarus in tows to
25 -30 m.,
Corroborative data on the upper depth distribution of these species
at night are given by other workers,
For example, Aron (1959, 1962)
noted peak abundance of L, leucopsarus and D, theta below 30 m off the
coast of Washington and in regions south of 50°N, but within the upper
30 m in more northerly regions; he also observed T. crenularis at the
surface under night-lights,
Tucker (1951) caught numerous L. leucopsarus
in a night tow to 37 m in the Bering Sea, and Fast (1960) considered
that the upper range of the adults of this species was about 50 m in
0
10
20
30
40
- 50
a-
W
100
Figure 4.
Depth variations in the catches of three lantern fishes at night, 50 miles off Newport, Oregon,
as a percentage of the total catch of each species (number in parentheses).
21
Monterey Bay, California,
Temperature and salinity profiles (Fig. 5) for the area where collections were made to successive depths show a thermocline located between 10
and 20 m and a halocline located between the surface mixed layer and 100 m.
The halocline, usually with its base at about 200 m depth, is a permanent
The
oceanographic feature in this area of-the Pacific (Fleming, 1958).
thermocline is well developed only in the summer (Tully, et al., 1960;
These density gradients result in high stability of the
Tabata, 1961).
water above 200 m.
Nevertheless, the dominant mesopelagic fishes migrate
through the base of the halocline and into the upper waters during the
night (see Fig. 2).
D. theta and T. crenularis apparently migrate through
the thermocline as well,
Thus these gradients do not necessarily act as
barriers to the mesopelagic fishes which swim vertically through, at least
one density gradient during their daily migrations into near surface
waters at night.
Depth distribution within the mesopelagic region was examined using
data from successive tows to 200, 500 and 1000 m.
Half the total number
of species of mesopelagic species was collected in night tows from 0-200 m.
These fishes that penetrated the halocline and invaded epipelagic waters
at night are considered upper mesopelagic species; they were largely
Myctophidae.
Species which were mainly restricted to tows to 500 m or
below and were uncommon above 200 m are considered lower mesopelagic
species; they were mostly Gonostomatidae, Chauliodontidae, Bathylagidae,
and some Myctophidae.
Some common lower mesopelagic species are listed in Table 2, which
gives numbers caught in tows to the different depths.
Note that
22
Table 2.
Catches of Some Lower Mesopelagic Fishes at the Stations
50 miles off Newport, Oregon.
Depth of Tows:
Number of Tows:
0-200 m
(46)
0-500 m
(17)
0-1000 m
(12)
Bathylagus milleri
0
5
4
Bathylagus pacificus
0
3
40
Searsidae
0
1
5
Cyclothone microdon
0
44
152
Cyclothone signata
0
119
119
Chauliodus macouni
11*
43
41
Lampanyctus nannochir
0
2
20
Lampanyctus regalis
1
7
12
Neoscopelarchoides dentatus
0
4
7
Poromitra crassiceps
0
1
14
* Mostly
small specimens.
TEMPERATURE °C
6.0
8,0
10.0
12.0
34.00
32.00
140
16.0
3600
SALINITY %bo
Figure 5.
A temperature and salinity profile, 50 miles off Newport,
Oregon, August, 1961.
23
relatively few individuals were taken within the upper 200 m, notwithstanding the much larger number of collections in this upper region.
Single
specimens of Talismania bifurcata, Macropinna microstoma, and unidentified
species of Cetomimidae and Oneirodidae were collected in tows to 1000 m
and are thought to be lower mesopelagic forms.
More collections of these
and other species are needed with opening and closing nets to establish
vertical ranges and changes in depth distributions during day and night
periods.
GEOGRAPHIC AND SEASONAL VARIATIONS
Collections of mesopelagic fishes along the three latitudinal series
of stations in the open ocean off Oregon revealed a similar species composition during all seasons of the year.
L. leucopsarus, D. theta, T.
crenularis and T. macropus predominated in nearly all collections within
the upper 200 m at night regardless of season of year or latitude.
Thus,
a single community of upper mesopelagic fishes was suggested by the
absence of drastic changes in the occurrence of species.
Some differences in distribution were apparent, however.
trends were related to latitude.
Several
The total number of mesopelagic species
collected increased at the stations to the south (Table 3), indicating a
higher diversity of the mesopelagic fish community at the lower latitudes
off Oregon.
Moreover, the relative abundance and frequency of occurrence
of several species of fishes were clearly higher off southern Oregon than
off northern Oregon.
These data suggest that Oregon is the northern limit
and zoogeographically a transitional area for some mesopelagic animals
(see also Aron, 1959, 1962).
24
Table 3.
(A) Total Number of Mesopelagic Species Collected and
(B) The Number/Occurrence of Four Species at the Three
Series of Stations off the Oregon Coast.
Columbia River
(A) Total Number of Species
Newport
Coos Bay
10
13
17
(26)
(46)
(29)
(B) Bathylagus ochotensis
2/1
9/8
23/14
Hierops crockeri
3/3
7/4
30/14
0
1/1
4/3
Number of Tows
Myctophum californiense
Lampanyctus ritteri
22/10
33/15
70/20
25
Collections along parallels of latitude across the continental slope
permit an examination of possible changes in the diversity of mesopelagic
fishes with increasing distance from shore.
In general both the total
number of species and the average number of species per collection were
lowest at the inshore stations and highest at an intermediate distance
from shore (Table 4).
Since Aron (1959) found that the number of species
of fishes decreased in oceanic water with distance from the Washington
coast, together these two studies suggest that the greatest diversity of
mesopelagic fishes may occur.,4over or just beyond the outer continental
slope.
Mesopelagic fishes were usually collected from the inshore stations,
A
across the continental slope, to the stations over 100 miles offshore.
notable exception, however, was the rarity of mesopelagic
species both in
number and kind, at the inshore stations off Newport (see Table 4 and
Fig. 6).
Although a considerable number of fishes were caught at stations
located 15 and 25 miles from shore along the northern and southern series,
they were rarely caught at the same distances off Newport despite numerous
collections.
The salinity at these stations off Newport is not greatly
modified by freshwater runoff; in fact, the inshore stations off the
Columbia River were most neritic in regard to reduced surface salinity.
In addition, mesopelagic fishes were absent from the inshore stations off
Newport even during periods of upwelling when the characteristics of the
water near the surface were more typical of-deeper, offshore waters.
An
obvious difference among the inshore stations is the depth of water.
Off
Newport the water is comparatively shallow.
Here the 200 m depth contour
occurs about 25 miles offshore, but it is found inshore of the 15-mile
26
Table 4.
Total Number of Species and the Average Number of Species
per Tow Collected at Various Distances from Shore off Oregon.
Distance Offshore
(n.m.)
Columbia River
Newport
Total Av./Tow
Total Av./Tow
Coos Bay
Total Av./Tow
15
3
1.8
1
0.1
7
4.0
25
8
3.3
3
1.1
8
5.4
45
7
4.5
10
4.8
13
7.0
65
6
4.2
11
4.8
6
5.5
65
4
4.0
9
5.2
11
5.7
Diaphus
Lam panyctus leucopsarus
46. 1 I'M
i
NEWPORT
COOS BAY
44-37'N
43' 2I' M
46'
COOS SAY
NEWPORT
ASTORIA - COLUM81A R1"E.R
ASTORIA-COLUMBIA RIVER
45. 2:'N
44' 37 N
N
28
23
14
JULY
AUG
NOV
DEC.
3
0
1-
JULY
12
43 24
16
C
B
e =
12
2
0
0
0
3
DEC
0
7
I-
5
5
w
-
0
1
2
FEB.
0
iI
I
MAR.
to
2
0
4
1
8
-S
2
0
UJ
!
FES
7
C
0 0
8
7
JAN
7
7
UJ
0
I
5
2
0
a
L.
I
16
1,
2
13
110
6
NOV
84
JAN. 0.1
AUG
22
LU
W
52 20
22 37
Q
7
6
0
O
e
0
0
0
O
O
35
W
APR.
p
APR
3
3
3
2
7
MAY
0
6
MAY
0
is
14
JUNE
1
O
2
JUNE
3
12
JULY
0
0
JULY
13
0
23
22
15
AUG.
2
25
45
65 85-165
0
15
0
25
AUG
45
65 85-165
MILES FROM SHORE
0
IS
25 45 65 85-165
0
15
25
45
65
85-165
0
t5
25
45
65 85-165
MILES FROM SHORE
Figure 6a. Average monthly catches of Lampanyctus leucopsarus at stations
various distances from shore along three latitudes off Oregon.
b. Average monthly catches of Diaphus theta at stations various
distances from shore along three latitudes off Oregon.
0
15
25
45
65 95165
27
Thus, depth appears
station at the latitudes of the other station series.
to be important in limiting the inshore distribution of these fishes, perhaps by affecting vertical migrations so that preferred light intensity is
simply not available during the day when the depth is less than 200 m, a
depth which interestingly conforms to the arbitrary division between
oceanic and neritic provinces of the
ocean,
This is evidence that these
fish are truly mesopelagic in distribution.
In order to examine seasonal changess,irt the distribution and abundance
of mesopelagic fishes, catches of the most common species were plotted for
various months of the
year.
These are illustrated for Lampanyctus
leucopsarus and Diaphus theta in Figures`).6a and 6b.
at inshore stations off
Newport,
Besides low catches
seasonal variations are apparent.
catches are usually highest during the summer.
summer periods that were sampled and for all
The
This was the case for both
latitudes,
with the exception
of the northern stations where peak catches of L. leucopsarus occurred
during the
winter.
The number of fish collected over the continental
slope during the summer was compared with that for the other months,-after
use of an X + 1/2 transformation
(Bartlett, 1947).
The average catch was
significantly higher during the summer khan during tie other seasons for
D. theta at all latitudes and for L. leucopsarus off Coos Bay (Table 5).
Such variations in numbers could be produced by selectivity of the
trawl combined with seasonal changes of population size-structure from
recruitment or
mortality.
A comparisQn between the size-frequency distri-
butions for summer and winter periods of both D. theta and L. leucopsarus,
however,
indicated that fish of various sizes contributed to the high
summer catches and that they were not solely a result of increased
28
Table 5.
Comparison of Average Summer (July-Sept.) Catches
With Average for Other Months for Two Species. Data
are Included From Stations 15-65 Miles Offshore,
Where Depth of Water Exceeds 200 m, at Three Latitudes off Oregon.
t
L. leucopsarus
D. theta
.98
3.02
d.f.
P
21 >0.3
21
( .01
Coos Bay
Newport
Columbia River
t
d.f.
t
1.49
20 >0.1
2.49
20
<.05
d.f.
P
3.41
22 <.01
3.79
22
<.01
29
vulnerability of young fish.
Seasonal differences in bathymetric distri-
bution may also affect catches if varying proportions of the populations
migrate vertically into the upper 200 m during different seasons of the
year.
Such a trend was not evident from the collections to 1000 m during
various seasons.
As data is limited, neither seasonal changes in popula-
tion size-structure nor depth distribution can be excluded from the analysis of these catch fluctuations, and both should be studied more thoroughly
as they may reveal salient features of the oceanic ecology of these animals.
Nevertheless, they do not appear to furnish a complete explanation to the
observed seasonal variations.
Hence, horizontal movements of the popula-
tions may also be important.
Only a few other studies on mesopelagic fishes have permitted comments
on seasonal changes in distribution.
Those of Barham (1956) and Fast
(1960), which were conducted in Monterey Bay, California, are of special
interest since they were concerned with the species which are also common
off Oregon.
Barham noted marked seasonal variations in the pattern of sonic
scattering layers and in the catches of certain midwater animals.
For ex-
ample, Diaphus theta, collected in high numbers in mid-winter when it was
thought to be a dominant sound scatterer, disappeared in the spring and
reappeared in the summer.
Fast reported high catches of Lampanyctus
leucopsarus in Monterey Bay in the winter with a reduction of the population by about one-half between February and May.
This was followed by a
subsequent increase in the first two age groups to high numbers by the
following February.
Finally, Taning (1918) found that large individuals
of Lampanyctus maderensis were absent from the eastern Mediterranean in the
summer but were common during other seasons.
These observations suggest
30
that seasonal changes in distribution of mesopelagic fishes may be influenced by population movements.
Horizontal movements may occur in two ways:
passively, by transport
with prevailing currents; or actively, by swimming of the micronekton
independently of currents.
Seasonal variations in depth distribution of
these mesopelagic animals, as observed by Taning (1918) and Barham (1956),
could result in translocation of the populations if current velocities or
directions vary at different depths.
The importance of vertical distri-
bution in influencing horizontal transport of plankton and micronekton is
well recognized (Hardy and Gunther, 1935; Mackintosh, 1937; Brunn, 1958).
To explain the fluctuations in number of L. leucopsarus in Monterey
Bay, Fast (1960) elaborated a hypothesis based on the seasonal oceanographic
periods and associated changes in current directions.
His highest catches
were made during the winter when prevailing winds are from the southeast
and the northward flowing Davidson Current is found along the coast of
California and Oregon.
The major reduction of the population occurred in
the spring after surface winds had shifted to a northwesterly direction
and upwelling was evident.
Fast attributed the high relative abundance
to the concentrating effect of the Davidson Current and the low relative
abundance the the dissipating effect of offshore drift during the upwelling
period.
Since he stated that the major differences between these two
periods were due to surface currents, the lantern fish presumably migrated
vertically into upper waters and resided there long enough to be transported by these superficial currents.
This hypothesis of passive transport of mesopelagic fishes was not
supported by the results off Oregon, where the highest catches appeared
31
during the summer, which is the period of upwelling, and lowest catches
The fluctuations were not similar to
appeared during the other seasons.
those found by Fast either in respect to time of year or oceanographic
periods.
Other hydrographic differences between these areas (see Sverdrup,
et al., 1942) may be involved.
The collections in Monterey Bay, California,
were made over a submarine canyon (a depth of about 900 fathoms), which
may act as a concentrating basin (Fast, 1960), whereas the collections off
Oregon were made in the waters off the unprotected coast, often where the
depth was less than 900 fathoms.
Only some northern stations off the
Columbia River were over a submarine canyon.
Clearly, before the effect
of currents on the distribution of these animals can properly be assessed,
more knowledge is needed on the seasonal variations of currents and
water masses at all depths within the vertical ranges of these species.
It is possible that active migrations of these micronekton may be a
cause of the seasonal fluctuations.
Virtually nothing is known about
lateral movements of small oceanic animals.
In general, extensive geo-
graphic migrations of nektonic animals on a seasonal basis as evidenced
for larger epipelagic fishes (e.g., Sette, 1950; Neave and Hanavan,
1960;
Clemens, 1961) are unexpected for mesopelagic micronekton because of
their relatively small size and slow swimming speed also because seasonal
variations of physical factors, such as temperature, are only pronounced
in the epipelagic zone. Small scale movements, however, across the
continental slope may be entirely feasible.
32
ACKNOWLEDGMENTS
The author is grateful to William Aron, M. Laurs, C. E. Bond, D. M.
Cohen, R. L. Wisner, B. N. Kobayashi, R. H. Gibbs, Jr., and A. Ebeling
who aided in identification of fishes; to L. D. Calvin for suggestions on
statistical procedure, and to L. Hubbard and the captain and crew of the
R/V ACONA for conducting the trawling operations at sea.
This study was
sponsored by the Atomic Energy Commission, Contract No. AT(45-1)1726.
Ship operations were supported by grants from the National Science
Foundation and Office of Naval Research.
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1960.
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Fleming, R. H., 1958.
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Hardy, A. C. and E. R. Gunther.
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1-146.
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Hedgpeth, J. W.
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Holme, N. A.
Classification of marine environments.
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Isaacs, J. D. and L, W. Kidd, 1953.
Isaacs-Kidd midwater trawl.
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Instit. Oceanogr, Ref. 53-3, 21 pp.
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Macmillan, 1-821 pp.
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Seasonal distribution of some
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Canada, 170221-233.
Osterberg, Charles,
1962.
Zn65 content of saips and euphausiids.
Limnol.
Oceanogr. 7:478-479,
------, W. G. Pearcy and H. C. Curl, Jr.
relationship to oceanic food chains.
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1958,
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Temporal changes of salinity, temperature, and
dissolved oxygen content of the water at Station "P" in the northeast
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Bd, Canada, 18:1073-1124.
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1918.
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1951.
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37
SPECIES COMPOSITION AND DISTRIBUTION OF PELAGIC CEPHALOPODS
FROM THE PACIFIC OCEAN OFF OREGON, 1961-1963
by
W. G. Pearcy
INTRODUCTION
To my knowledge there are no previous reports on the cephalopods in
the Pacific Ocean off Oregon.
Much of our present knowledge about the
species composition and distribution of cephalopods of the Pacific Ocean
is the result of the cruises of the ALBATROSS, Steamer of the U. S. Fish
Commission, made during the late nineteenth and early twentieth centuries.
ALBATROSS collections along the west coast of North America were mainly at
stations off California and Central America or off Alaska; but comparatively few collections were made off Oregon (Townsend, 1901).
Neither
Holye (1904) nor Berry (1912) list any cephalopods taken at ALBATROSS
stations off Oregon or Washington.
Clearly, data on pelagic cephalopods
is desirable to enable comparisons of fauna and generalization on zoogeographic distribution,
METHODS
A total of 385 collections made between June 1961 and July 1963 with
a six-foot Isaacs-Kidd midwater trawl from the R/V ACONA, provided most of
the data on pelagic cephalopods collected off the Oregon coast.
Collec-
tions were made at a series of stations located 15, 25, 45, 65, and between
65 and 165 miles offshore along three latitudes off Oregon (Fig. 1) during
the night within the upper 200 m (depth permitting).
Generally, the
38
stations off the central Oregon coast (Newport) were sampled every month,
whereas, the other stations were sampled bimonthly.
In addition to the 0-200 m epipelagic collections at various distances
from shore, tows were made to provide data on the depth distribution of
cephalopods.
Over one hundred collections were made to three successive
depths(200, 500, and 1000 m) at a station 50 miles off Newport, Oregon,
over the outer edge of the continental slope.
(For more details on methods
see Section 1,)
Midwater trawl collections were preserved with formalin at sea.
Cephalopods were removed, sorted, identified and dorsal mantle length
(DML) measured in the laboratory ashore.
Besides the midwater collections, cephalopods were collected occasionally with dip nets under lights at night.
Some squid were also captured
using otter trawls,
RESULTS
The families and species of pelagic cephalopods collected off Oregon
are listed in Table 1.
These include 17 species, representing 12 families.
Seven of these species represent new distributional records for the northeastern Pacific Ocean,
Only eight are included in Berry's (1912) "Review
of the Cephalopods of western North America," a review based mainly on
bottom collections,
The additional species included in this paper clearly
indicate the value of midwater trawling in any survey of cephalopod fauna.
Although most of these species were collected in the midwater trawl,
several were captured by other methods.
For example, the two Moroteuthis
robusta examined (DML 650 and 1350 mm) were captured in otter trawls off
WASHINGTON
1-
165
85
65
45
25(15
ill, 19
AS roR I A
OREGON
85
165
65
15
NEWPORT
85
165
"-
45
25 15
/
128°
Figure 1.
65
/J
?
COOS BAY
CALIFORNIA
126°
Location of midwater trawling stations off the Oregon coast.
Numbers denote distance in nautical miles from shore. The
circle at 50 miles off Newport includes the location of tows
to various depths.
39
Table 1.
List of Pelagic Cephalopods Collected from the Pacific Ocean
off Oregon.
Loliginidae
Loligo opalescens Berry, 1911
Sepiolidae
Rossia pacifica Berry, 1911
Onychoteuthidae
Onychoteuthis banksi (Leach, 1817)
Moroteuthis robusta (Dall) Verrill, 1876
Enoploteuthidae
*Abraliopsis sp.
Veranyidae
*Octopoteuthis sicula Ruppell, 1844
Histioteuthidae
Gonatidae
Chiroteuthidae
Meleagroteuthis holyei Pfeffer, 1900
Gonatus fabricii (Lichtenstein, 1818)
G. magister Berry, 1913
*G. anonychus Pearcy and Voss, 1963
*Gonatopsis borealis Sasaki, 1923
Chiroteuthis veranyi (Ferussac
1835)
Cranchiidae
Galiteuthis armata Joubin, 1898
*Taonius pavo Lesueur, 1821
*Cranchia scabra Leach, 1817
Vampyroteuthidae
*Vampyroteuthis infernalis Chun, 1903
Octopodidae
Bolitaenidae
Japetella heathi (Berry, 1911)
* Not previously reported from the northeastern Pacific.
40
the northern Oregon or southern Washington coast in water greater than 150
m depth,
This species has been reported from California (e.g., Smith, 1963)
and Alaska (Dall; see Berry, 1912) but none have been reported previously
off Oregon.
Loligo opalescens, a common inshore myopsid of the west coast
of North America, was collected in several otter trawl collections where
depth was 100 m or less.
It was absent from midwater trawl collections,
which were mainly made offshore in deeper water.
Rossia pacifica, another
myopsid, was also taken mainly in otter trawl collections.
Gonatus
anonychus, a new species of gonatid squid, recently described by Pearcy
and Voss (1963), was collected by dip netting under night-lights.
The relative abundance of the cephalopods collected by midwater
trawling from all stations and all depths is shown in Figure 2.
Gonatus
fabricii was by far the dominant species, comprising,about 38 percent of
the total catch.
Gonatus spp, was next in numberical importance.
This
group consisted of larval and juvenile individuals without sufficient
differentiation of hooks for specific identification.
They may comprise
at least three separate species of Gonatus (see Table 1), but judging from
the relative abundance of larger gonatids, are probably mostly G. fabricii.
Abraliopsis sp. and Chiroteuthis veranyi were next in numerical abundance
(Fig. 2).
Four squids, Gonatus fabricii, Gonatus spp., Abraliopsis sp.,
and C.
veranyi, comprised about 88 percent of the total numbers of pelagic
cephalopods collected, clearly demonstrating their dominance in our midwater trawl collections off Oregon.
lected,
Only a few other species were col-
PERCENTAGE OF TOTAL CATCH
0
1
Gonatus
fabricii
Gonatus
s pp.
10
20
30
I
I
I
Abra/iopsis sp.
Chiroteuthis veranyi
Japete//a heathi
Gonatopsis borealis
Octopodidae
Teonius pavo
Gonatus
magister
Ga/iteuthis armata
Octopoteuthis sicu/a
Onychoteuthis banksi
0
Q
Rossia p aci fica
Vampyroteuthis infernalis
Cranchia scabra
0
Me%dgroteuthis ho/ye/
fl
Figure 2.
a
The relative abundance of pelagic cephalopods found off Oregon in midwater trawl
samples, expressed as percentage of the total number of animals collected.
41
Geographic Distribution
No differences in the basic species composition of cephalopods was
noted among the three latitudinal series of stations off Oregon.
Similar
species composition was indicated for all latitudes and most stations from
15 to 165 miles offshore.
Pelagic cephalopods were rare, however, at the
inshore stations off Newport, Oregon, where the depth of water
than 200 m.
was less
A similar paucity of mesopelagic fishes was noted in neritic
waters off Oregon (Section 1).
Depth Distribution
Some features of the depth distribution of the cephalopods collected
are summarized in Table
hour of towing (Table
The number of dominant squid captured per
2.
2A)
was greater in tows to 200 m than in deeper
tows, particularly for Gonatus spp., Chiroteuthis veranyi and Abraliopsis
sp.
Most of these animals found in tows to 500 and 1000 m were probably
Such differences
caught while the trawl sampled through the upper 200
m.
in catches suggest that the four dominant squids (G.
fabricii, Gonatus
spp., Abraliopsis sp., and C.
tion.
However,
veranyi)
are mainly epipelagic in distribu-
most of the 0-200 m collections were made
during the
night.
Comparisons of day and night catches of Gonatus fabricii and
Abraliopsis (Table
2B)
show that higher catches were made during the
night than during the day.
This indicates either daily vertical migration
or better visual avoidance of the trawl during the day.
these squids in tows to 500 m, on the other
day.
These opposite
trends,
hand,
Catches of both
were highest during the
with an increase in catches at depth during
42
Table 2.
Average Number of Pelagic Cephalopods Collected, per Hour of
Trawling in Tows of Various Depths.
0-200 m
0-500 m
0-1000 m
72 tows
23 tows
24 tows
Gonatus fabricii
Gonatus spp.
Chiroteuthis veranyi
Abraliopsis sp.
0.5
1.2
0.5
0.7
0.5
0,2
0.1
0.1
0.1
0.1
0.1
0.1
(B) Day-night catches for two
species:
Day Night
Day Night
Species
(A) Four dominant species:
Gonatus fabricii
0.2
0,6
0.7
0.2
Abraliopsis sp.
0.0
0.7
0.2
0.1
(C) Some lower mesopelagic
species:
Japetella heathi
Octopoteuthis sicula
Galiteuthis armata
Taonius pavo
0.03
0.00
0.00
0.01
0.21
0.04
0.04
0.14
0.14
0.02
0.05
0.06
43
the day, support the contention of diurnal vertical migrations of these
species,
Some of the cephalopods usually inhabited waters below 200 m.
All
the species listed in Table 2C were most abundant in deep collections.
No large individuals were taken above 200 m even at night, suggesting
that these have a basically mesopelagic (200-1000 m) distribution (also
see Sasaki
(1929)
for G.
armata).
Vampyroteuthis infernalis was also
taken only in deep tows to 1000 m and never in tows that went only to 500 m.
Seasonal Variations
Although
no prominent changes in species composition were apparent
over the two-year period for which samples have been
analyzed,
seasonal
differences in relative abundance of pelagic cephalopods were striking.
During the summer the number of animals
magnitude
higher
than
per tow was about an order of
during the other
months.
Table 3 compares the
average number of dominant species collected per tow for the summer months
with the non-summer
months.
The catch of G. fabricii was about eight
times higher during the summer, Gonatus and C, veranyi about six times
higher,
Such seasonal differences are of interest since they indicate marked
changes in the availability of cephalopods.
Such differences could be due
to changes in susceptibility to capture or changes in actual abundance of
cephalopods.
In either case, the differences could be related to the life
history of the squid.
examined.
Consequently, size-frequency distributions were
44
Table 3.
Seasonal Occurrence of Common Cephalopods in 0-200 m
Collections.
Average Number per Tow
July-Sept.
Oct.-June
(79 tows)
(205 tows)
Gonatus fabricii
4.9
0.61
Gonatus spp.
1.9
0.32
Chiroteuthis veranyi
0.71
0.20
Abraliopsis sp.
1.9
0.33
45
The size-frequency distributions for Abraliopsis (Fig.
ing,
They indicate
that
3)
are reveal-
during the summer the catch of this species con-
sisted mainly of small individuals (less than 30 mm
the other seasons larger squid
predominated.
DML),
whereas, during
These differences indicate
that breeding in Abraliopsis is probably restricted to one
season.
Catches
of larger animals may be lower during non-summer seasons because of better
escapement and lower abundance following early mortality,
The relative
the larval
distribution of sizes of G. fabricii (assuming most of
Gonatus are G.
for the two periods (Fig.
fabricii),
on the other
are very similar
hand,
suggesting that the summer increase in catch
4),
is not merely the result of the recruitment of
young.
The fact that during
July-September 21 percent of the animals were over 30 mm in mantle length,
whereas only 7 percent were over 30 mm from October-June suggests an actual
increase in the abundance of larger G. fabricii during the summer.
Such
variations may be due to changes in abundance caused either by ocean circu-
lation or actual movement of the squid.
DISCUSSION
Some squid are notoriously fast swimmers; others are soft bodied and
more planktonic than nektonic,
Obviously such differences in swimming
ability determine the catch composition by any sampling method.
Many times
during this study Onychoteuthis banksi (greater than 130 mm DML) were ob-
served around night-lights, but they were rarely captured in midwater
trawl collections made at about the same station and time.
cephalopods collected in the midwater trawl were small.
captured was a Gonatopsis borealis of 250 mm DML.
Most of the
The largest animal
G. borealis and Gonatus
46
magister over 200 mm in mantle length were most common in the otter trawl
collections and several large Moroteuthis robusta (up to 1350 mm DML) were
taken by this method.
The distribution of a species also effects its availability to
sampling devices.
Since most of the midwater trawl collections were made
over the continental slope in the upper 200 m at night, obviously coastal,
epibenthic or deep-sea species will not be adequately represented.
For
example, although Rossia pacifica was frequently collected with a bottom
trawl over the shelf, it was rare in midwater trawl collections over the
slope.
Another species, Loligo opalescens, was only taken in inshore otter
trawl collections.
The dominant type of squid was collected by two independent sampling
devices off Oregon--the midwater trawl and albacore tuna.
Of the cephalopods
found in the stomachs of 66 albacore collected during the summer of 1962,
small gonatids also predominated.
As predators often obtain effective
samples of cephalopods (Clarke, 1963), this agreement was encouraging.
Comparisons of the fauna found off Oregon with adjacent regions at
present would be premature due to our lack of knowledge.
Such comparisons,
however, would be of particular interest as correlated with the oceanography
of the North Pacific,
As the West Wind Drift (Subarctic Current) approaches
the North American continent, it divides to form the California Current and
Alaskan Gyral off the coast of Oregon and Washington.
Hence, the oceanic
fauna from Oregon is suspected to show relationships with regions in the
same current system to the west and to the south.
The ocean off Oregon is
a transitional region, consisting largely of modified Subarctic water.
The proportion of equatorial water increases with depth and varies
JULY-SEPTEMBER
Abraiiopsis s p.
J:ffi
I0
Figure 3.
ri 0--H
n A=
20
30
40
SIZE (MANTLE LENGTH IN mm )
50
Size-frequency distributions of Abraliopsis found in midwater trawl samples
during the summer (July-September) and other seasons of the year (October-June).
60
25 t-
Gonatus fabricii
Gonotus larvae
20E
a
15 -
10p
OCTOBER - JUNE
Gonotus
15t-
fabricii
Ek
Gonotus larvae
10
5
0
Figure 4.
10
20
30
SIZE (mm)
40
50
60
Size-frequency distribution of Gonatus fabricii and Gonatus larvae found in midwater
trawl samples during the summer (July-September) and other seasons of the year
(October-June).
47
seasonally (Tibby, 1941; Rosenberg, 1962).
These oceanographic features are useful in interpreting the distribution of oceanic cephalopods.
For example, McGowan and Okutani (1963)
reported that the two most abundant species of squid larvae off California
(Abraliopsis sp, and Gonatus fabricii) were most frequently collected in
waters that showed a high percentage of northern(Subarctic) origin (or a
low percentage of equatorial water).
These two squids, as we have seen,
are also the most abundant in our catches.
The capture of Vampyroteuthis
infernalis off Oregon, a species predominantly found in the deep water of
tropical and subtropical oceans and not known beyond 400 latitude (Pickford,
1946), also corresponds to the presence of a high proportion of equatorial
waters found in deep waters off Oregon.
REFERENCES
Berry, S.
S.
1912,
A review of the cephalopods of western North America.
Bull. U.S. Bur, Comm. Fish. 30:269-336.
Clarke, M. R.
1963,
Proc. XVI Int. Congress of Zool. 1:67.
samplers,
Hoyle, W. E.
Information obtained by using squid predators as
1904,
Reports on the Cephalopoda.
Bull. Mus, Comp. Zool,
43(1):1-71.
McGown, J. A, and T. Okutani,
1963,
The distribution and abundance of
the epipelagic decapod (Cephalopoda) larvae in the California Current.
Proc. XVI Int. Congress of Zool. 1:68,
Pearcy, W. G, and G. L. Voss.
the northeastern Pacific,
1963,
A new species of gonatid squid from
Proc. Biol. Soc. Washington 76:105-112,
48
Pickford, G. E.
1946.
chiate cephalopod.
Vampyroteuthis infernalis Chun, an archaic dibranI.
Natural history and distribution.
Dana Rept.
No. 29:1-40.
Rosenberg, D. H.
1962.
Characteristics and distribution
off the Oregon coast.
M.S. Thesis.
of water masses
Oregon State Univ. Library.
1929. A monograph of the dibranchiate cephalopods of the
Sasaki, M.
Japanese and adjacent waters.
J. Fac. Agric. Hokkaido Univ. 20(Suppl.):
1-357.
Smith, A. G.
1963.
More giant squids from California.
Calif. Fish and
Game 49:209-211.
Tibby, R.
B.
1941.
The water masses off the west coast of North America.
J. Mar. Res. 4:112-121.
Townsend, C. H.
1901,
Dredging and other records of the United States
Fish Commission Steamer ALBATROSS, with bibliography relative to the
work of the vessel.
Rept. of Comm., U.S. Commerce of Fish and
Fisheries, Pt. 26:387-562.
1Fy
NOTES ON THE OCCURRENCE AND DISTRIBUTION OF MACROPLANKTON
OFF THE OREGON COAST
A, EUPHAUSIIDS by J. F. Hebard
This paper constitutes a preliminary examination of the species and
distribution of euphausiids off Oregon.
Euphausiid shrimp play an important role in the economy of the sea,
both as food for the larger nektonic forms (fish, squid, etc.) and as
consumers of the smaller plankton forms (small crustaceans and phytoplankton),
Euphausiids are also known to undertake extensive vertical
migrations; however, little is known about their lateral movements.
often constituted the bulk of midwater trawl samples off Oregon.
They
Moreover,
Euphausia pacifica is known to concentrate certain radionuclides and has
been used as a standard in several radioecological studies (Osterberg, et
al,, Section 6 and 7).
Along the coast of Oregon, the environmental conditions vary during
the year,
Upwelling,of deep, cold oceanic water into the surface layers
is brought about by the action of prevailing northwesterly winds during
summer,
Also, the Columbia River introduces large quantities of fresh
water into the surface waters during this time of the year.
It is not
known what influence such environmental changes have in altering the
distribution of euphausiid shrimp,
Results
Of the euphausiids collected (see previous sections for methods), a
total of eight species were identified,
Only three of these species were
abundant; the other five were sporadic in occurrence and never were
50
abundant.
These eight species are listed below in order of numerical
abundance in midwater trawl collections.
1. Euphausia pacifica
2. Thysanoessa spinifera
3, Thysanoessa longipes
4, Nematoscelis difficilis
5. Tessarabrachion oculatus
6, Stylocheiron abbreviatum
7e Nematobrachion flexipes
8, Stylocheiron maximum
Examination of the average relative abundance of the six common
species in collections from the three latitudes, indicated a decrease in
For some of these species
numbers from south to north (Table 1),
pacifica and T.
spinifera)
(E.
there was also a trend toward decreasing abundance
offshore.
The catches of euphausiids varied with season.
was about an order of magnitude
ample,
the
The biomass of
summer.
highest
during the
E. pacifica
summer,
euphausiids,
numerous in the winter than in
on the other
hand,
was generally
months,
which constituted a major portion of the
Hence,
seasonal differences in the abundance
of E. pacifica and other species may be related to annual cycles
life
history,
in their
as well as to changes in hydrographic conditions.
Some general features of the distribution of these
from Brinton
for ex-
This was mainly due to the presence of large
(p 2.0 cm in length)
catch during the summer
more
T. spinifera,
(1962)
are as follows:
species,
taken mainly
51
Table 1,
Average Abundance of Euphausiids per Tow at Three
Latitudes off Oregon.
Columbia River
Newport
Coos Bay
E. pacifica
2,4
3.3
3.8
T, spinifera
0.6
1,0
3,1
T, longipes
0,6
0.7
1.1
N, difficilis
0,1
0,2
0.9
T, oculatus
0,0
0,2
0,2
S, abbreviatum
0,0
0,0
0,2
52
Euphausia Pacifica - This species, which was abundant off the Oregon
coast most of the year, is a subarctic and transitional water species found
over most of the North Pacific Ocean and southward along the North American
coast as far as Baja, California.
The Davidson current, a subsurface,
northward flowing, winter current along the coast of the western United
States, may carry eggs and young E. pacifica northward, thereby maintaining
the coastal populations of this species off,Oregon.
This species is pri-
marily found in the upper 300 m, but may occur in small numbers below 300 m
in particular conditions.
Thysanoessa spinifera - This species is primarily a neritic species
found in the Gulf of Alaska and farther to the south along the coast of
North America.
According to Brinton, concentrations of this species have
been associated by our own data, however.
Vertically, T. spinifera is
apparently limited to the upper 100 m.
Thysanoessa longipes - This species is restricted to the North Pacific
Ocean up to and including the American Arctic.
The southern oceanic limit
is at approximately 40°N but extends to northern California in the eastern
North Pacific.
Vertically, T. longipes is primarily a surface form.
Nematoscelis difficilis - They are found in a belt like distribution
across the North Pacific in the North Pacific Drift and in the California
Current which flows south along the coast of North America.
Its range in
the coastal North American waters is more extensive than in the Western
Pacific.
It is rarely found in cold, upwelled water off Oregon, Washington,
or northern California.
Nematoscelis difficilis is most common above 140 m,
Tessarabrachion oculatus - This species is confined to the subarctic
North Pacific with a southward extension of the range of the west coast of
53
the United States,
In vertical distribution, the adults are found at all
depths sampled except at southern limits of the range where it disappears
from the surface,
Stylocheiron abbreviatum - These species have been found in the subtropical and tropical waters between the subtropical convergences (40°N
and 40°S) with the exception of the eastern equatorial region,
It is an
offshore, warm water species in the region of the California Current.
They are collected between 50 and 300 m depth and apparently do not undertake any vertical migrations,
Nematobrachion flexipes - Although reported from the coastal waters
of Alaska and British Columbia, this species is a tropical and subtropical
species,
Adults undertake some vertical migration being mainly at 280-700
m during the day and above 280 m at night,
This species and S. abbreviatum, which are primarily subtropical
species, are not normally found off Oregon.
Thus they may be useful as
indicators of the origin of coastal waters.
Stylocheiron maximum - This is a large mesopelagic species found
northward into the Gulf of Alaska as well as in the central and equatorial
regions of the Pacific,
Adults of this species are rarely found above 140
m depth and are caught in great numbers only below 500 m.
REFERENCES
Brinton, Edward,
1962.
The distribution of Pacific euphausiids.
Scripps Institution of Oceanogr. 8:51-270.
Bull.
55
OCEANIC NATANTIA (PENAEIDEA AND CARIDEA) by Carl Forss
B.
Since 1961 the Department of
Oceanography,
Oregon State University,
has undertaken an intensive study of the fauna and ecology of oceanic and
mesopelagic waters off the coast of
work several species of
like forms) have been
macurous
obtained.
Oregon.
During the course of this
decapod Crustacea (shrimps and shrimp-
This paper is a preliminary report on
some of the Natantia (Penaeidea and Caridea).
4.4
For details on the collection methods, see Section 1.'
RESULTS
The most common species of natant shrimp was Sergestes similis.
It
accounted for the bulk of specimens collected over the continental slope
off Oregon,
The catches of this species tended to decrease with distance
from shore off Coos Bay and Astoria,
However, an increase in the catches
was noted offshore from Newport (Table 2), with the highest catch per tow
(64) being found the farthest distance from the coast,
S. similis occurred
mainly in the upper 200 m collections and catches decreased rapidly with
depth (Table 3).
Hence this species, which has a transparent,
membranous
exoskeleton, was found near the surface in epipelagic waters, at least at
night,
S, similis is known to range throughout the north Pacific from
Japan to Washington as far south as the Gulf of California,
Most of the specimens of S. similis were comparatively small, ranging
from 10 to 18 mm in carapace length (tip of rostrum to posterior margin of
carapace) with the carapace length of 12 mm appearing most frequently,
seasonal distribution pattern for S. similis has not been definitely
A
Table 2.
Catches of Some Natant Decapod Crustacea off the Oregon Coast in 0-200 m Midwater
Trawl Collections.
Coos Bay
Newport
Mi les Off shore
Species
15
25
45
Sergestes similis
35.0
19.0
20.0
Astoria
Miles Of fshore
65
9.2
Mi les Of fshore
15
25
45
65
15
15.0
29.0
22.0
64.0
17.0
4.2
0.7
2.4
0.1
0.4
0
0
1.4
0
0
25
45
65
Gennadas sp.
0.1
0
0
0
0
0
0
0.1
Pasiphaea pacifica
2.7
0.2
0
0
0
1.4
0
0
Pandalus sp.
0
0
0
0
24
0.8
0
0
1.0
0
0
0
Hymenodora frontalis
0
0
0
0
0
0
0
0
0.8
0
0
0
625
501
376
4516
16
16
'17
70
Total number of
species caught at
each station
Total number of hauls
at each station
345
9
97
9
181
9
46
5
55
886
72
9
12
12
'12
19
8
57
Table 3.
Catches of Oceanic Natantia in Tows to Various Depths at NH-50
0-200 m
(118 tows)
Species
Number
of
Number
Gennadas sp.
38
0.04
Number
of
(28 tows)
Number
4543
5
13
366
0.3
9
Pasiphaea pacifica
.03
1
Pandalus sp_
.07
2
.96
1.9
.03
Parapasiphaea sp.
.07
Hymenodora frontalis
Hymenodora gracilis
Number
of
.03
Number
tows
tows
tows
Sergestes similis
0-1000 m
0-500 m
(28 tows)
2
1
1.9
27
54
1
54
.60
17
Acanthephyra curtirostris
.03
1
.14
4
Notostomus elegans
.07
2
.03
1
Systellaspis cristata
.03
1
Systellaspis affinis
.03
1
Systellaspis braueri
.17
5
58
established, but during the summer months it was noted that the larvae exceeded the adults in number, especially for the month of August (Fig, 1).
This shows that the high numbers found in the summer were due to larval or
juvenile animals, probably the result of breeding earlier in the year.
It
is interesting to note that Barham (1956) concluded from the abundance of
young found the year around the S. similis spawned more than once a year.
Pandalus sp, was only common at the inshore station off Newport,
which is the only station over the continental shelf,
They were rare
Two species of Pasiphaea were identified, P. pacifica, which
offshore.
is common in catches, and P. chacei,
Pasiphaea like Pandalus appeared to
be an inshore species, occurring most. abundantly at station AH-20 (Table
2),
Based on the catches to various depths (Table 3), it was concluded
that several species of shrimp were mesopelagic (200-1000 m) in distribution,
1000 m.
Gennadas was found almost exclusively in tows to depths to 500 or
Both Hymenodora frontalis and the less frequent H. gracilis were
also collected mainly in tows to 500 or 1000 m.
The remaining oplophorids
(Acanthephyra, Notostomus and Systellaspis) were found only in tows to 500
or 1000 m.
2000
Sergestes sirni/is
LARVAE
ADULT
1000
0
JUNE
JULY
AUGUST
1961
Figure 1.
The distribution of adult and larvae forms of Sergestes
similis for June, July
and August 1961.
59
SALPS by Lyle Hubbard
C.
Five species of salps representing five genera were found off the
Oregon coast.
vagina
These species are Helicosalpa virgula
Tilesius, 1802,
(Pallas,
1774)
Salpa fusiformis
Cuvier,
(Vogt, 1854)
1804, Iasis zonaria
and Pegea confoederata (Forskol, 1775).
were based upon Yount
(1954).
Thetys
Identifications
Dr. Yount also verified our identifications
from specimens sent to him.
It should be noted that the data for 1961-1962 is based on counts
from subsamples (split counts), while that for 1962-1963 is based on the
number of salps from the entire sample (whole counts).
Species Distribution
The distribution of salps, both by the number of species and the number
of individuals, appeared to vary with latitude.
As shown in Table 4, the
largest number of salps species per station during the two years was consistently found off Coos Bay (CH) or the southern stations.
The second
highest number of species were found off Newport (NH), while the lowest
number of species was noted off Astoria (AH).
On the basis of the number
of salps per tow, Coos Bay was again the highest followed by Newport; the
lowest number of salps per tow was found at the northern area or stations
off Astoria.
Thus there was a trend for more species and higher catches
to the south of the Oregon coast,
H. virgula was recorded only once in our tows.
captured at CH-45 in March 1962,
second year (1962-1963).
Two individuals were
It did not make an appearance in the
60
Thetys vagina was recorded at Coos Bay and Newport for 1962 and 1963
only.
It did not appear off Astoria.
Both solitary individuals and chains
of the aggregate form were noted.
Pegea confoederata made a single appearance off Coos Bay in 1961-62,
but occurred off Newport and Astoria in 1962-63, failing to show on the
Coos Bay stations.
Iasis zonaria was found off Newport in 1961-62 and off Newport and
Coos Bay the following year.
It has not been caught off Astoria to date.
Salpa fusiformis is the only form that has been found with regularity
along all three lines of stations during both years.
The echinate form of
this species (S. fusiformis aspera Ihle,l911) has not been separated from
the non-echinate form due to taxonomic difficulties.
Seasonal Occurrence
The abundance of salps off the Oregon coast (Fig. 2) seemed to vary
by the season with peak numbers during the spring and summer months.
Their
occurrence the rest of the year was irregular.
Peak abundance was noted between May and August for both years.
The
two years were not comparable on the basis of the number of salps collected:
1962-63 appeared to be a "salp" year compared with 1961-62.
After September the number of salps generally decreased until the next
May, sometimes not making an appearance for a month or more.
Salps were
noted early in March for both years followed by low numbers in April.
On February 2, 1963, a large number (31) of Pegea confoederata were
captured at NH-15.
Helicosalpa virgula made its only recorded appearance
in our catches in March 1962.
Aside from the general salp peak in the
134
2592
b.
100
Cl.
WHOLE COUNTS
SPLIT COUNTS
1728
1 Solp count in, tow
Tow -no salps
o
3
0
Far
w
a
25
0
0
0
S
1961
Figure 2.
N
0
J
F
M
A
1962
M
411l1;1
J
A
1
0
S
1962
Salp catch as recorded by the midwater trawl (1961-1963).
J
F
1,
I
M
A'
1963
1111
1
M
Distribution of Salps off the Oregon Coast as Determined by Midwater Trawling.
Table 4.
WHOLE COUNTS (July 1962--June 1963)
SPLIT COUNTS (July 1961--June 1962)
15
25
45
65
65+
15
25
45
65
65+
0
0
123,60
0
0
0.42
4.47
2.83
0
0
No. tows
5
5
5
3
7
7
6
3
2
No, spp.
0
1
0
0
1
1
1
0
0
4.57
2.00
370,28
288.00
4.22
1.08
0.70
21.33
0
3
Stations,
1
AH- (Astoria) ,
Av. no./tow
NH (Newport)Av. no./tow
No, tows
7
7
8
7
6
9
12
10
12
No. spp.
0
1
1
1
1
2
1
1
4
Av. no./tow
180.80
161.60
171.20
234.00
52.00
15.00
12.00
19.80
0.40
0
No. tows
5
5
5
4
2
5
5
5
4
2
No. spp.
1
1
2
1
1
2
3
3
1
0
CH (Coos Bay)
62
spring and
summer, February
peak, especially
and March must also be considered as a secondary
for "rarer" species appearing
off the
Oregon coast.
REFERENCES
Yount, James.L.
1954.
The taxonomy of the salp ideal (Tunicata) of the
central Pacific Ocean.
Pac. Sci., Vol. V171, No. 3, pp. 276-330.
63
D. MEDUSAE, SIPHONOPHORES. AND CHAETOGNATHS by R. W. Renshaw
The medusae, siphonophores, and chaetognaths captured by the midwater trawl have been analyzed.
The medusae and siphonophores, because
of their gelatinous structure, were not sampled adequately and cannot be
treated thoroughly in this report.
A few generalized statements about
the medusae will be made later in the paper.
The siphonophores were represented off the Oregon coast by 13
species
(Table 5).
in seasonal
There did not appear to be any indication of changes
occurrence except for the condrophore Velella velella, which
appeared off the coast in the spring.
There was some evidence of differ-
ences in vertical distribution, but without an opening-closing mechanism
(which has recently been added to the trawl) any statement would be premature and must await further investigation.
The chaetognaths were represented in the samples by 11 species
(Table 5).
Two species, Sagitta macrocephala, and Eukrohnia fowleri, are
mesopelagic species and were only caught in 1000 m tows.
of these two species had a red pigmented gut.
All specimens
For most species the data
does not indicate seasonal change, or the data were too incomplete to
show any change.
An inverse relationship between Sagitta scrippsae and S. euneritica
is suggested, which was correlated with oceanographic seasons.
S.
scrippsae is an oceanic species that is most abundant in the West Wind
Drive and California Current.
On the other hand, S. euneritica is a
neritic species extending from Baja, California, to as far north as 46
14.5'N (approximately the Washington-Oregon border).
Figure 3A compares
the abundance of S. scrippsae and S. euneritica in our inshore collections, 15 miles off the Oregon
coast, during
January.
S. euneritica
appears to be much more abundant inshore than S. scrippsae, particularly
at northern stations.
This indicates more oceanic influence at the
southern stations than the northern stations.
A similar trend is sug-
gested in Figure 1B where S. scrippsae is more abundant 45 miles offshore than S. euneritica, except at the northern station (46°14'N).
At the intermediate station (44°38N) S. scrippsae is more abundant than
it was at 15 miles offshore.
These data suggest that at southern latitudes (43°20'N) there is a
greater oceanic influence than at northern stations,
Moving north the
oceanic influence decreases and there is a spreading of the neritic environment further offshore.
Figure 3A is for January and indicates little,
if any, subarctic influence along the Oregon coast at this time.
during the summer (July)
scrippsae increased (Fig.
abundance.
S. euneritica decreased in abundance whereas S.
3B)
and other subarctic species reached maximum
For example, S. elegans,
a subarctic
chaetognath,
was abundant
during the summer and was virtually absent during winter months.
medusae, Aglantha
However,
digitale,
The
another subarctic species, was also most
abundant during the summer months (July and August).
It was rarely cap-
tured in the winter.
The medusae were represented by 11 species (Table 5).
Several other
species may be present but the condition of the specimens is such that
identification is impossible.
Of those medusae that have been identified,
Atolla vanhoeffeni and Periphylla periphylla were the most abundant.
Without exception, they were captured on every tow.
One medusae,
b.
1000
0 S. euneritica
1000
S. scri ppsae
45 MILES
15 MILES
500
X
L11
m
z
n
0
<j
430 20 N
_
440 38'N
f
460 14` N
0
430 20' N
44° 38'N
Figure 3. Catches of two chaetognaths during January 1962, at three latitudes off Oregon.
(b) 45 miles offshore
(a) 15 miles offshore
460'14! N
65
Table 5.
A List of Species of Siphonophores, Chaetognaths,
and Medusae Captured off the Oregon Coast.
Siphonophora
Vogtia spinosa
Nectodroma dubia
N. reticulata
Lensia conoidea
Sulculcolaria quadrivalvis
Chelophyes appendiculata
Physophora hydrostatica
Bargmannia sp.
Chuniphyes multidentata
Muggiaea atlantica
Nanomia bijuga
Velella velella
Chaetognatha
Sagitta bierii
S. decipiens
S. euneritica
S. elegans
S. macrocephala
S. minima
S. scrippsae
S. zetesios
Eukrohnia bathypelagica
E. fowleri
E. hamata
Medusae
Aglantha digitale
Colobonema sericeum
Crossota rufobrunnea
Pantachogon haeckeli
Halistaura cellularia
Aeguorea sp.
Aegina citrea
Solmissus marshalli
Atolla vanhoeffeni
A. wyvillei
Periphylla periphylla
66
Colobonema sericeum appears to be amesopelagic species.
It was only
captured when the trawl net was fished to 500 or 1000 m.
If plankton animals may be used as hydrographic indicators, the
above data suggest that during the winter the influence of subarctic
water is at a
minimum,
while in the summer months subarctic water is
at a maximum off the Oregon coast.
changes in water masses off Oregon.
Such data are useful in showing
Hence seasonal variation in the
abundance of certain oceanic animals may be directly related to the
circulation off
Oregon.
For instance,
the high catches of fishes and
squids in the summer may be affected by movement of water as well as
movement of the animals themselves.
67
VERTICAL DISTRIBUTION OF THE NUMBERS AND BIOMASS OF
MESOPELAGIC FISHES WITH AN IMPROVED ISAACS-KIDD MIDWATER TRAWL
by
W. G. Pearcy
INTRODUCTION
The Isaacs-Kidd midwater trawl or IKMT (Isaacs and Kidd, 1953) is
recognized as one of the most useful devices for sampling small nekton
and macroplankton over a wide range of depths in the ocean (Aron, 1962;
Foxton, 1963).
It has two serious inadequacies, however, for most eco-
logical research; neither quantitative estimates of the density of catch
or information on depth distribution are provided by the unmodified trawl.
Quantitative estimates of pelagic animals require knowledge of the
volume of water filtered by the sampler.
This is complicated by the
presence of three different mesh sizes in the IKMT, each having a dif-
ferent filtration and selection characteristics (see Aron,
1959).
Informa-
tion on the depth of animals collected requres some means of opening
closing the trawl.
Several methods have been attempted for the IKMT.
and
A
Leavitt-type releasing device was employed by Kelly (1958, 1961) in which
the mouth of the trawl was initially pursed, and messengers actuated
opening and closing of the cod-end of the trawl at depth.
Disadvantages
of this method are the notorious unreliability of the Leavitt system
(Yentsch et al., 1962; Currie, 1962; Foxton, 1963) and the fact that some
water is being filtered during descent of the trawl (Kelly, personal
communication).
68
The most notable advance is the recent development of catch-dividingbucket (Currie, 1962; Foxton, 1963), which automatically diverts the catch
from one cod-end net to another at a selected depth, thus giving two samples per tow.
The cod-end nets are 6 feet long to provide flow of water
through the bucket.
In this paper several innovations to the Isaacs-Kidd midwater trawl
were employed to study a specific problem:
the general features of the
vertical distribution of mesopelagic fishes within the upper 1000 m.
The
results are preliminary.
METHODS
Several modifications of the IKMT were made to improve it for quantitative sampling at various depth intervals.
None of these improvements
required any independent development, only the adaptation of products
already commercially available.
A Lamont Multiple Plankton Sampler (MPS) was adapted as a cod-end
collecting unit for the midwater trawl.
one a side, was used in this study.
A scaled-down model, 13 inches
Opening and closing operations took
place at the preselected depths of 150, 500, and 1000 m during the descent
of the trawl.
This device employs a pressure-sensitive release mechanism
which releases three rotating bars at preset depths, thus opeing and
closing the nets and sampling within three successive depth layers (Be,
1962).
The pressure-release system was calibrated by the manufacturer.*
Lowering the device vertically (wire angle <5°) to various depths at sea
showed the nets closed between 150-160 m, 480-520 m, and 940-960 m, respectively.,
* G. M. Mfg. Co., 12 East 12th St., New York, N. Y.
69
To reduce the problems associated with different mesh sizes in the
trawl net, the entire body of the net was lined with a 3/8" (squared
measure) knotless nylon.
Hence, with exception of the #0 plankton net
in the collecting nets of the MPS, only one mesh size was used.
A depth-distance recorder, mounted on a stay in the mouth of the
trawl (Fig. 1),
gave estimates
within each depth interval.
of the
distance
the trawl traveled
According to the manufacturer,** the error
of the depth-distance recorders, determined by pressure testing in the
laboratory, is t 3 percent of the maximum depth.
sea gave comparable depth variations.
Our field testing at
The recorder has horizontal fins
and is self-adjusting for pitch
Figure 2 duplicates the trace from a typical tow.
The trawl descends
at 30 m of wire/minute while the ship is underway at about 5 knots.
first
net,
The
which is open on the way down, is closed and the second is
opened at 150 m
depth.
The second net is closed and the third opened at
500 m, and the last net closed at 1000 m depth.
It is important to note
that the trace is approximately a straight line within each depth interval, 0-150, 150-500, and 500-1000 m; this indicates that nearly equal
volumes of water were fished at all depths within each layer.
(If the
trawl does not fish all depths equally and animals are not distributed
uniformly within
depths,
estimates of abundance may be seriously biased.)
Assuming that the flow of water through the depth-distance recorder
applies to the entire mouth of the trawl, then the volume of water
filtered can be calculated within each depth interval as a product of
the cross sectional area of the trawl (2.89m2, as estimated by planimetry
** Tsurumi Precision Instruments Co.,
Japan.
Ltd.,
1506 Tsurumi-Machi, Yokohama,
70
and triangulation) and the distance traversed within each depth layer.
The most serious problem encountered during sea trials with the
modified trawl was insufficient flushing of the contents of the trawl
past the MPS into the collecting nets.
After tows to 1000 m depth, the
net, which ascends with the cod-end open, frequently had animals adhering
to the trawl netting.
They were articularly concentrated toward the end
of the trawl just before the attachment of the MPS.
This indicated that
animals were not immediately passing through the trawl netting.
Thus,
animals accumulating in the trawl at one depth layer were a source of contamination for nets open at lower depths.
The flushing of the midwater trawl was improved by the following
modifications: (1) a knotless nylon liner was used instead of the knotted
netting;
(2) the midwater trawl net was tailored with a gradual taper to
the MPS eliminating the looseness produced when the 1/2 m cod-end diameter
was constricted over the MPS; (3) a plastic (Herculite) collar was added
to the end of the trawl to further reduce pockets for accumulation of
animals and furnish a better means of attaching the MPS to the trawl;
and (4) to increase the flow of water through the MPS while sampling,
a six-foot section of 3/8" knotless nylon was added between the MPS frame
and the plankton nets.
With these changes, contamination was markedly reduced.
Providing
sufficient flow of water through the opening-closing device will undoubtedly
be a problem common to all cod-end units (see Foxton, 1963).
Some contam-
ination is unavoidable since time is required for organisms to pass through
the net.
It can be minimized when flow is accelerated or the time fished
at each depth layer is prolonged, i.e., when the ratio, flushing time/
Figure 1.
Isaacs-Kidd midwater trawl showing the depth-distance
recorder mounted on the depth depressor.
DISTANCE
2
3
4
5
MILES
IN
6
7
8
9
10
II
I-
a
W
a
1 000
Figure 2.
Duplication of a trace made with the depth-distance recorder
on a tow which sampled three depths within the upper 1000
meters.
71
fishing
for a net is low.
time,
The weight of the MPS was originally thought to pose an added flushing
problem by sinking relative to the end of the
trawl.
However, the low
specific gravity of the PVC frame and the hydrostatic pressure of the
water maintained the MPS at the same level as the trawl.
Operational success of the MPS-IKMT unit has been
total of 30 separate tows to 1000 m
attempted,
samples, $1 samples from discrete depths were
ures (10
percent)
good.
Out of a
which should give 90
All of the fail-
obtained.
were because the deep net (500-1000
m)
did not close.
The presence of water inside the cylinder may have caused the failures so
an addition at "0" ring was installed around the piston. Ridges in the
cylinder,
which also may have prevented a full stroke of the piston, were
Since these minor structural changes, all nets have,closed.
ground down.
Collections with the MPS and IKMT for study of the vertical distri
bution of biomass and numbers of fishes were generally made over a 24-48
hour
period,
providing both day and night collections for each depth layer.
All the collections reported on here were made in the vicinity of 44°37'N,
125°15'W, 50 miles off Newport,
Oregon,
over the outer continental slope.
Geographic fixes were recorded at the beginning of each tow and when the
trawl was at each closing depth, assuming a wire/depth ratio of 4:1 (see
Pearcy, Section 1).
not
available,
On the January
series,
and the distances towed-were
a depth-distance recorder was
approximated,
using the geo-
graphic fixes and correcting for the difference between the position of
the vessel and the
trawl.
Since Backus, Hersey
(1956)
and Mead (1963)
found that the cable of the IKMT was nearly straight during towing, these
differences were determined by simple triangulation.
72
After each tow the net was thoroughly washed by towing beside the
vessel and by use of fire hoses.
formalin in sea water.
Collections were preserved at sea with
Fishes were removed from the collections, weighed
after removal of excess water (wet weight), identified, and counted.
RESULTS
The number and biomass of fishes collected per 1000 mJ within each
depth interval are summarized as histograms for three series of collection
made during different seasons during the year (Figs. 3 and 4).
Each
series includes collections made during day and night periods.
A general pattern of bathymetric distribution of fish numbers is
evident for each of the three series of collections (Fig. 3).
During the
day, maximum numbers were found at mid-depth (150-500) for all series,
and relatively few fish were found in surface waters (0-150 m) or below
500 m.
During the night, i.e., tows initiated after sunset, the maximum
numbers of fishes occurred in surface waters.
In all instances,
catches
in deep water (500-1000 m) were lowest.
The diel diurnal variations within each series indicate an increase
in the numbers found in surface waters at night, a feature that has been
commonly observed in the past.
But the corresponding decrease in the
numbers at mid-depths has rarely been documented.
Both changes are posi-
tive evidence of vertical migration of these mesopelagic fishes within the
upper 500 m.
There are no consistent trends shown that suggest any diel
change in numbers below 500 m, as numbers are uniformly low during both
day and night periods.
Thus, there is no evidence for vertical migration
below 500 m from these data.
7-8 JANUARY 1963
TIME"
0753-1102
1249-1612
C.-150
1822-2134
0.6
150 - 500
2358 - 0309
(:7
2:0
0.5
500 - I OOC
05
0:5
28-30 APRIL 1963
V)
x
W
TIME
0658-0857
07
0-150
1250 -f635
1_3
0.2
0.8
0.3
0.4
T
03
02
1
1
150-500
Z
=
500-1000
I
L
CL
W
8C7-2018
0030 - 0235
0.9
0
?-8-30 AUGUST 1963
TIME'
0536-i324
1
630 - 1845
i 7'2-1920
2317-0;4C
00'5 - 0240
0-150
150-500
500-1000
0.9
0.4
1
Figure 3.
I
Histograms showing the number of fishes captured per 1000 m3 of water filtered within
three depth intervals for collections over day and night periods.
7-8 JANUARY 1963
TIME:
0753-1102
1249-1612
X822-2134
0-150
2358 - 0309
1.8
50-500
38
28-30 APRIL 1963
TIME
0-150
065E-0857
125..-635
18C
.0.5
I
0030-0235
0.7
23
.50-500
56
z
28-30 AUGUST 1963
TI ME ;
C3+-1322
237 -C i
82
50C
0.4
I
Figure 4.
84
08
001 5 - 024C
199
3f
56
76
05
86
1
Histograms showing the wet weight of fishes collected per 1000 m3 of water filtered
within three depth intervals for collections over day and night periods.
73
Similar trends are apparent from the catches expressed as biomass
of fishes per 1000 m3 for the various depths (Fig. 4).
Usually the
weight of fishes was highest at mid-depth during the day and lower in
surface waters and deep waters.
However, in some cases the trends are rather variable,
night, for example, maxima appear at all depths.
During the
The lack of.a large
surface maxima during the January series may have been caused by a_full
moon which surpressed the ascent of fishes.
The biomass in 500-1000 m
collections was usually low and no..day-night differences were evident.
The occurrences were evident.
The occurrence of high biomass in deep
water in the last series was surprising after the low values found in
earlier collections.
In both cases, these high weights shown for. 500-
1000 m in Figure 4 were caused by.a.few large fishes.
Differences in the vertical-distribution of number and biomass are
interesting.
Diel variations were evident.in both the 0-150 and 150-500 m
depth intervals in numbers, but only between 0-150 m in the biomass.
Moreover, the decrease in the numbers of fishes at mid-depth between day
and night periods was not evidence in fish biomass.
Hence a decrease in
number was apparent at night between 150 and 500 m, oddly enough with no
corresponding decrease in weight.
The standing crop of fishes
per
m2
surface area through a column
1000 m deep was calculated for all series by multiplying the average
catch per
m3
times the depth of the
the three layers.
shown on the 1000
3.3.
interval
and summing the values for
This merely is a weighted average of the estimates
m3
basis.
The number of fish per m2 ranged from 0.6-
2
Biomass was between 1.1 and 7.6 g per m.
These estimates, which
74
are considered first
approximations,
for the standing crop of mesopelagic
are the only ones to my knowledge
fishes.
Of interest is the fact
that the biomass of these small oceanic fishes is about the same as the
estimates of biomass per m2 of pelagic fishes in the English Channel
(Harvey, 1950).
Day-night differences in average catches per m2 in Table 1 indicate
that usually fishes were more numerous
in night tows.
fish biomass was collected per m2 at night.
In all
series more
This indicates.tha't collec-
tions during darkness are more effective in capturing mesopelagic fishes
within the upper 1000 m.
The day/night ratio of b.iomass was lower than the day/night ratio
of numbers except for the January series, indicating that there ,was- a
greater increase in weight than in numbers in the night samples.
In
other words, the average size of fish captured at night was larger than
in the day (Table 1).
This difference explains the seemingly paradoxical
decrease in numbers at mid-depth with no apparent decrease in biomass.
At night, larger fish made up a significant portion of the biomass though
few in number.
DISCUSSION
It has been known for a long time that more micronekton and macro-
plankton are collected during the night in upper ocean waters than during
the day.
nized:
Two explanations for this phenomenon commonly have been recog-
(1) vertical migration of animals below sampling depths during
the day, and (2) better visual avoidance of nets during the daylight hours.
If all depths through which the nets are towed are not sampled equally,
75
Table 1.
Number and Weight of Mesopelagic Fishes Collected per
m2 (to 1000 m depth) and Average Size of Fishes (g/m)
for Three Series of Collections.
January 7-8,
April 28-30,
Night
Day
Date:
Day/Night
1963
No./m2
1.2
1.0
0.9
1.1.
1.10
G/m2
1.7
1.8
2.1
2.1
0.83
G/no.
1.4
1.8
2.3
1.9
No./m2
0.7
0.6
0.2
1.4
0.36
G/m2
1.8
1.1
1.2
6.3
0.22
G/no.
2.6
1.8
6.0
4.5
404
408
1963
August 28-30, 1963
No./m2
2.2
2.4
2.1
3.3
1.8
0.87
G/m2
1.3
7.6
2.6
5.2
7.4
0.61
G/no.
0.6
3.2
1.2
1.6
4.1
76
an added possibility exists, namely that day and night differences are
merely an artifact due to preferentially sampling depths where animals
are concentrated during the night.
This latter possibility is minimized
when all depths are sampled equally by a net, e.g., oblique tows.
Several examples of these day-night differences found in oceanic
animals of the northeastern Pacific are pertinent. Tucker (1951) noted
that the large increase in the number of lantern fishes captured in surface waters during the night was not accompanied by an equivalent decrease
in the numbers found deep waters off San
Diego, California.
He noted that
the difference between the number of fishes captured during day and night
periods may have been caused by ascent at night from depths below 600 m,
the maximum depth of his
McAlister
(Tucker's) trawling.
(1961)
observed
that the weight of plankton collected with half-meter nets from 300-500 m
was about the same for both day and night periods, but five times more
was collected in the upper 300 m during the night than during the day.
Aron
(1962)
also found that night collections caught substantially more
biomass than day collections.
The results of King and Iverson
(1962)
on the catches of pelagic
fishes by midwater trawling in the Central Pacific demonstrated that
night collections took about four or five times the volume but only 2.5
times the number of fishes as the day catches.
Such differences between
volume/number ratios indicated that, on the average, larger fishes were
captured at night.
This is similar to the results I have reported.
As both vertical migration and the ability of animals to avoid the
collecting net are influenced by submarine light intensity, their effects
on diel variations of catch are difficult to
discriminate.
This is
77
especially true if sampling is not carried out below the day depth of
the migratory animals.
In all of the above mentioned studies, sampling
or less.
was restricted to 600 m depths
Therefore, it was recognized
by these authors that the high catches at night could be caused by either
migration of animals from below the maximum sampling depth or by net
avoidance.
If migration during the day to depths lower than 500 m is, the sole
explanation of the differences in catch,, then we would expect to find
an increase in the numbers and biomass of fishes collected between 500-.
1000 m during the day.
substantial proportion
intensity,
even larger
trawl than in overlying
In
most cases cited, this must necessarily be a
of the
animals.
At these depths of,low.,light
fishes should be'less-able to visually avoid the
waters.
Off Oregon, catches below 500 m were generally low in numbers: and
biomass.
There
500 and 1000
vals.
were indications
of diel variations in number between
m, as were observed in the 0-150 and 150-500 m depth inter-
Consequently, even though there was good evidence for vertical
migrations above 500 m, the simplest explanation for the day-night differences in numbers and weight of fishes per m2 is better visual avoidance
of the trawl within the upper 500 mduring the day, particularly by the
larger fishes.
SUMMARY
(1) A new method is described for quantitatively sampling difference
depth intervals with the Isaacs-Kidd midwater trawl.
78
(2) Diel vertical migration is reflected by the increase in the
number of fishes collected per 1000 m3 from 0-150 m at night and the
decrease from 150-500 m during the day.
(3) There was an increase in the biomass of fishes captured at night
in surface waters (0-150 m), but no- apparent differences below 150 m.
(4) The biomass,and especially the number of fishes found below
500 m, were low compared to overlying waters.
(5) There was no apparent day-night difference in the number and
biomass of fishes below 500 m.
biomass and number of fishes captured per m2_surface area
.(6) The
(to 1000 m depth) were almost always greater at night.
fish also was greater at night.
catches per
The average size
Thus, the major diel differences in
can be most readily explained. by better visual.avoidance
m2
of the trawl within the upper 500 m during the day than during the night.
REFERENCES
Aron, W.
1959.
Midwater traveling studies in the North Pacific.
Limnol. and Oceanogr..4:409-418..
-------
1962.
Some aspects of sampling the macroplankton.
Rapp. Proc.
Verb. Cons. Int. 1'Explor. Mer. 153:29-38.
Backus, R. H. and J. B. Hersey.
1956.
Echo sounder observations of
midwater nets and their towing cables.
Be, A. W. H.
samplers.
CurVie, R.
I.
1962.
Deep Sea Res. 3:237-241.
Quantitative multiple opening-and-closing plankton
Deep Sea Res. 9:144-151.
1962.
Net closing gear.
l'Explor. Mer. 153:48-54.
Rapp. Proc. Verb.
ons. int.
79
Foxton, P.
An automatic opening-closing device for large plankton
1963.
nets and midwater trawls.
Harvey, H. W.
1950.
Plymouth.
J. Mar. Biol. Assoc. U. K. 43:295-308.
On the production of living matter in the sea off
J. Mar. Biol.
Isaacs, J. E. and L. W. Kidd.
Assoc. U. K. 29:97-137.
Isaacs-Kidd midwater trawl.
1953.
Scripps
Inst. of Oceanogr. Ref. 53-5, 18 pp.
Kelly, G. F.
Woods Hole Laboratory, U.S. Fish
In.annual report.
1958.
and Wildlife Service, June 30, 1958, pp. 29-33.
1961. Vertical distribution of young redfish
and A. M. Barker.
in the
Gulf,
of Maine.
Rapp. Proc. Verb. Cons. Int. 1'Explo-r. Mer.
150:220-233.
King, J. E. and R. T. B. Iverson.
1962.
Midwater trawling for forage
1951-1956.
organisms in the Central Pacific.
U.S. Fish and Wildlife
Service Fish Bull. 62(210):271-306.
McAllister, C. D.
1961. Zooplankton studies at the ocean weather station
"P" in the Northeast Pacific Ocean.
Mead, G. W.
1963.
Observations on fishes caught over the anoxic waters
of Carioca Trench, Venezuela.
Tucker, G. H.
1951.
Deep Sea Res. 10:251-257.
Relation of fishes and other organisms to the
scattering of underwater sound.
Yentsch, C.
J. Fish. Res. Bd. Canada 18:1-29.
J. Mar. Res. 10:215-238.
S., G. D. Grice and A. D. Hart.
1962.
Some opening-closing
devices for plankton nets operated by pressure, electrical and
mechanical action.
153:59, 65.
Rapp. Proc. Verb. Cons. Int. 1'Explor. Mer.
81
NOTES ON THE VERTICAL DISTRIBUTION OF ZINC-65 AND ZIRCONIUM-95 FROM
OCEANIC ANIMALS
by W. G. Pearcy and C. L. Osterberg
INTRODUCTION
The potential role of animals in modifying the distribution of
radionuclides by their own movements has been clearly recognized.
Migrations may result in a net transport of elements from areas of
high concentration to areas of low concentration in horizontal and
vertical directions.
Vertical transport of radionuclides is
of`
singular importance because animals making daily vertical migrations
are abundant in the oceans.
Moreover, their movements frequently
penetrate density gradients that impede physical mixing of surface and
subsurface waters.
Vertical transport by such animals may equal or
exceed transport of radioisotopes by physical processes (Ketchum and
Bowen, 1958).
This paper includes some preliminary data on the concentrations
of two radionuclides in marine animals from various depths: zinc-65
and zirconium-95-niobium-95.
Zinc-65 is produced mainly from neutron
activation of Columbia River water by nuclear reactors.
a fission product entering the ocean,from fallout.
Zr95-Nb95 is
These radionuclides,
as well as other gamma emitters, have been previously reported from
pelagic animals off Oregon (Osterberg, et al., Sections 6 and 7).
82
METHODS
Animals were collected with an Isaacs-Kidd midwater trawl (mesh
size 1/2" stretch) using a Lamont Multiple Plankton Sampler as an
opening-closing unit, thus providing samples from three depth intervals:
0-15Q m, 150-500 m, and 500-1000 m,
The volume of water fil-
tered was estimated from the cross-sectional area of the mouth of
the trawl and the distance towed at each depth interval as determined
from geographic fixes (see Section 4 for details).
Four tows, two
during the day and two during the night, 50 miles off the central
Oregon coast (44°37`N, 125°15`W) during January 7-8, 1963, provided
the material radioanalyses.
Whole samples of animals, consisting of a mixed species composition, were weighed (wet-preserved weight), ashed at 450°C, and packed
in 15 cc plastic counting tubes, reweighed and sealed.
Samples were
then placed in the well of a 5" x 5" Harshaw Nal crystal and analyzed
with a gamma-ray spectrometer (512 channel nuclear data model 130A)
according to the method of Perkins (1958) and Covell (1959).
time was either 100 or 200 minutes, depending on sample size.
Counting
Counts
were converted to picocuries per entire sample, per gram and per 1000
m3 water filtered.
RESULTS AND DISCUSSION
The data on the picocuries of Zn65 and Zr95^Nb
weight and wet weight are given in Table lA and 1B.
95
per gram of ash
The total varia-
tion in the concentration of Zn65 was small, ranging from 11.9 to
83
42.9
pc/g ash and
0.4-2.1
pc/g wet
weight.
The average Zn65 content found
in animals from the four series of collections for each depth interval,
0-150 m, 150 -500 m, and 500 -1000. m,; indicated
on an ash weight basis and 1.1:
1.2:
ratios of l
2.1:
1.0 on a wet weight basis.
1.0
This
indicates little variation in the average concentration,of Zn65 in the
animals with depth.
most as much Zn65
Animals from deep water
per gram as animals
(500-1000 m) contained al-
above 500 m.
The concentrations of Zr95-Nb95 on the other hand, showed a much
wider variation, 7.I-269'4 pc/g ash and 0.4-7.2 pc/g wet. weight.: Much
of this variation appears to be related to the depth of capture of the
animals.
The ratios for Zr95-Nb95 with depth are 9.0:
ash weight basis and 5,,4:
0.7:
1.1:
1.0 on an
1.0 on,a wet weight basis for the.,0--150
m, 150-500 m, and 500-1000 m collections, respectively.
These differences
indicate that the concentration of this radionuclide is about 5 to 9 times
higher in the animals collected at the surface (0-150 m) than at the
greater depths.
Undoubtedly, some of the differences between the trends shown on an
ash weight and wet weight basis are. due to the type of animals collected.
For example, during the day surface catches often consisted of a higher
percentage of gelatinous or watery forms (medusae, salps, chaetognaths);
hence, the ash weight/wet weight ratio may be much:.:lower than at night
when animals like euphausiids are common in surface waters.
The differences in the concentration of these two gamma emitters with
depth agree with the conclusion of Osterberg et al. (Section 6) that particulate fallout isotopes such as Zr9S-Nb95 showed prominent spectral
peaks only in
filter-feeding heribores and were not concentrated
appreciably
84
Table 1.
Concentration of Zn65 and Zr95-Nb95 in the Samples of Oceanic
Animals from 0-150,, 150-500, and 500-1000 m in Depth,
Collected January 7-8, 1963, 50 miles off Newport, Oregon.
standard counting error.
Zn65 and Zr95-Nb95/g ash
Zn65 and Zr95-Nb95/g wet weight of sample.
water filtered.
g wet weight of animals per 1000 m
A.
B.
C.
(picocuries)
A.
Zn65/g ash
0-150 m
150-500 m
500-1000 m
42.9
42.4
19.9
18.9
0.8
1.3
10.5
53.8
11.9
5.8
1.2
1.2
39.8
44.2
14.8
2.0
1.2
1.2
36.3
28.3
34.1
1.0
0.8
1.3
128.5
30.4
8.4
7.0
1.1
2.8
138.9
19.1
15.4
5.0
1.0
1.3
55.7
17.1
34.8
1.0
0.7
1.4
Zr95-Nb95/g ash
0-150 m
150-500 m
500-1000 m
B.
269.1
11.8
38.4
0.7
7.1
1.3
Zn65/g wet weight
0-150 m
150-500 m
500-1000 m
1.00
1.89
1.42
0.42
1.79
0.71
2.07
1.00
0.75
1.89
1.48
2.12
7.22
2.90
0.89
2.17
13.96
7.28
2.32
Zr95-Nb95/g wet weight
C.
0-150 m
6.27
150-500 m
0:53
5.19
1.01
500-1000 m
0.51
0.50
0.43
0.78
1.20
7.97
3.30
6.66
8.57
2.62
g wet weight/1000 m3
1.08
6.89
1.66
85
by higher trophic
levels.
which is ionic in sea water
Whereas Zn65,
(Greendale and Ballou, 1954), was concentrated by all animals analyzed
off
Oregon.
surface
A lower Zr95/Zn95 ratio was expected in deep water than in
water, therefore,
because most of the deep animals were carnivores.
The vertical distribution of
Zn65 and Zr95-Nb95
per volume of water
is graphically shown in Figure 1 for each of the three depth layers.
concentration of these two radionuclides was calculated
from:
The
pc/1000 m3
(pc/g ash)(total g ash)/1000 m3 filtered.
The histograms ofZn65 (Fig.
LA)
During the day the total amount of
face layers is very low.
increase
reveal several interesting features.
Zn65
in midwater animals from the sur-
At night, however, there is an order of magnitude
Although Zn65 per gram wet
in the Zn65 of these upper waters.
weight may be somewhat higher in animals collected at the surface at night
(Table
1B),
this cannot explain the large increase in radiozinc.
It is
mainly due to the high biomass in the upper 150 m at night and the paucity
of animals at this depth during the day (Table 1C).
Consequently,
much of
the Zn65 measured appears to be incorporated in small nektonic and large
planktonic animals that undertake vertical migrations into the upper 150 m
at night.
The vertical flux of
Zn65
indicated here may actually be a low
estimate because a full moon during the night period probably suppressed
the ascent of animals during the night (see
The trends of
Zn65/ 1000 m3
Pearcy,
Section 4).
at mid-depths (15Q-500
though less
are also correlated
spectacular than those observed in surface
waters,
with diel variations of biomass
The observed
(Fig. 1).
m),
decrease in
Zn65
at mid-depths during the night is expected if animals ascend from this
layer into surface
waters.
The fact that 150-500 m biomass (g/ 1000
m3
86
in Table 1C) does not demonstrate an apparent decrease at night is most
simply explained by the capture of larger animals during the night when
their ability to avoid the trawl is reduced compared to periods of daylight
(see Pearcy, Section 4).
These larger animals captured at night in mid-
depths appear to have a lower concentration of Zn65/ g wet weight (Table 1
and Appendix I) than those which migrate nightly into surface waters.
The
concentration of Zn65 in deep water (500-1000 m) is relatively low and
uniform in Figure 1.
The amount of Zn65 found in the midwater animals off Oregon calculated
per m2
in a column
1000
histograms in Figure 1.
m deep was 5.9, 6.2, 6.1, and 10.2 pc for the
The variability of these values is less than that
found between samples at any one depth.
Histograms showing the vertical distribution of Zr
95-Nb 95
(Fig. 1)
are more difficult to interpret due to the variability found among depths.
Still, the Zr95-Nb95/1000 m3 demonstrates appreciably day-night difference
in surface waters (0-150 m).
tion of animals.
This again may be related to vertical migra-
The amounts of this radionuclide in the day collections,
however, were 2.7 and 4.6 pc/m2 compared to 9.5 and 7.4 pc/m2 for collections during the night.
night.
Thus over twice as much was collected per m2 at
Such a difference, as well as the lack of evidence for any in-
crease in Zr95-Nb95 during the day at mid-depths, suggests that other
factors may play a role in affecting the diel and vertical variations of
this radionuclide.
An explanation for this difference is that the availability of
animals that accumulate Zr95-Nb95 may vary within the sampling period.
For example, it has been noted that the biomass of animals per m2 captured
DAY
N
I
GHT
Zn65/ IOOOm3
5l.
2
z
.5
0.5
1
- 500
Co - 000
Zn65/m2
64
1
130
[1421
86
24
2.4
2:0,
4.9
5.9
6.2
6.1
10.2
108
Zr95 - Nb95 / 1000 m3
r
.1-150
58
162
481
,5C-500
3.6
80
3.7
T.
0.8
500 - 1000
c
Zr95-Nb95/ mZ
Figure 1.
2.7
I
4.6
176
65
zo
9.5
7.4.
Zn65 and Zr95-Nb95 contents in pelagic animals for day and night periods, January 7-8,
1963, 50 miles off Newport, Oregon.
87
during the day in tows to 1000 m is often less than the biomass collected
at night.
In the case of fishes, this is due primarily to the presence of
larger animals in night collections, animals which may avoid the trawl in
the day.
Similar trends with plankton, such as euphausiids, suggest that
they also demonstrate day-night changes in availability, perhaps due to
more effective escapement during the day.
Thus day-night differences in
the catch of herbivores like euphausiids, which have been found to accumulate particulate fallout radionuclides like Zr95-Nb95 more than carnivores
(Osterberg, et al., Section 6), may be particularly important in affecting
our estimates
of Zr95-Nb95/1000 m3
Another possibility is that there may be diel differences in the
actual amount of Zr95-Nb95 found in the animals.
Zr95-Nb95, unlike Zn 5,
is not metabolically active and probably passes directly through the digestive tract.
(Chipman, 1958).
for instance, was rapidly excreted by copepods
As a result, animals actively feeding in upper waters
at night may have peak Zr95-Nb95 concentration at this time of day.
Although this suggestion is not corroborated by the variations
g (Table
1),
of Zr95-Nb95
it requires further study.
SUMMARY
Zr95-Nb
1.
The concentrations of two gamma emitters, Zn65 and
95
were examined in pelagic animals collected at three depths, 0-150, 150-500,
and 500-1000 m, using an opening-closing unit on a midwater trawl.
2.
Zn65/g wet weight of sample was about the same at all depths,
whereas Zr95-Nb9S/g was about five times higher above 150 m than in deeper
water.
88
3.
The Zn
65
in animals per 1000 m3 water filtered was highest in
This
the upper 150 m during the night and in mid-depths during the day.
was mainly due to vertical migrations of animals.
4.
The highest values for Zr95-Nb95/1000 m3 also were found during
the night in surface waters.
5.
The amounts of Zn65 and Zr95-Nb9S per m2 (to 1000 m depth)
were 5.9-10.2 and 2.7-7.4 picocuries, respectively.
REFERENCES
COVELL, D. F.
1959.
Determination of X-ray abundance directly from the
total adsorption peaks.
Anal. Chem. 31:1785-1790.
GREENDALE, A. E. AND N. E. BALLOU.
1954.
Physical state of fission
product elements following the vaporization in distilled water and
seawater.
CHIPMAN, W. A.
organisms.
U.
S. Navy Res. Def. Lab. Doc. 436, pp. 1-28.
1958.
Accumulation of radioactive materials by fishery
Proc. 11th Gulf & Caribbean Fish. Inst.,
KETCHUM, B. H. AND V. T. BOWEN.
97-110.
1958. Biological factors determining
the distribution of radioisotopes in the sea.
In:
Proc. 2nd
U. N. Int. Conf. on Peaceful Uses of Atomic Energy, 18:429-433.
PERKINS, R. W.
1958.
Gamma-ray spectrometric systems of analysis.
In:
2nd U. N. Int. Conf. on Peaceful Use of Atomic Energy, 28: 455-461.
89
Concentration of Several Gamma Emitters in Nine Species of
Mesopelagic Fishes Collected on December 7, 1962, at a Station
50 Miles off Newport, Oregon
Appendix 1.
K40
pc
A.
Zn65
std
std
error
error
pc
Ru-Rh
Zr95-Nb95
pc
error
std
std
std
pc
error
pc
error
Upper Mesopelagic Fishes, collected above 200 m at night
Lampanyctus ritteri
pc/g ash
pc/g wet
56.6
1.7
2.0
26.7
0.8
4.2
106.7
3.3
26.5
103.5
3.2
27.0
49.5
20.4 201.6
6.1
20.1
0.5
74.3
151.6
3.5
75.4
1.1
51.0
1.2
12.0
4.6
2.7
34.9
0.9
4.6
56.1
1.5
28.5
55.8
28.5
79.2
1.8
55.5
1.1
4.9
98.5
2.3
102.1
2.1
29.4
36.7
4.0
3.4
1.1
0.1
14.8
11.2
0.3
wt.
Diaphus theta
pc/g ash
pc/g wet wt.
6.9
Lampanyctus leucopsarus
pc/g ash
pc/g wet
23.2
0.6
wt.
Tactostoma macropus
44.9
pc/g ash
pc/g wet wt. 1.0
34.4
pc/g ash
pc/g wet wt. 0.7
7.4 151.4
4.1
8.0
8.2
79.6
1.8
90.5
1.8
2.3
66.7
2.4
2.5
5.0
1.5
30.5
121.8
2.8
129.3
29.8
30.9
2.6
Tarletonbeania
crenularis
pc/g ash
pc/g wet
23.1
wt.
9.9
7.3
2.5
39.6
12.6
4.3
B. Lower Mesopelagic Fishes, collected in tows to below 500 m depth
Chauliodes macouni
31.8
pc/g ash
0.6
pc/g wet wt.
72.2
1.4
3.7
51.9
1.0
8.4
142.4
2.8
52.7
174.8
3.5
54.0
Poromitra cristiceps
30.7
55.9
pc/g ash
0.9
pc/g wet wt.
80.5
1.3
6.7
25.1
0.4
11.1
256.0
4.1
52.6
144.5
2.3
45.3
Lampanyctus nannochir
33.3 14.5
pc/g ash
pc/g wet wt. 0.7
43.0
0.9
3.6
40.2
0.9
8.4
214.7
4.7
52.9
197.5
4.4
53.8
Bathylagus sp.
25.0
pc/g ash
0.9
pc/g wet wt.
26.8
0.9
2.3
30.8
1.1
4.5
56.9
1.9
23.0
101.4
21.4
13.9
10.3
3.5
91
RADIOACTIVITY AND ITS RELATIONSHIPTO OCEANIC FOOD CHAINS
by
Charles Osterberg, William
G,
Pearcy,_-and Herbert
Curl, Jr.
ABSTRACT
Gamma-ray spectra of some primary producers (single-celled plants),
filter-feeding
I, II,
III,
herbivores, and carnivores,
and III-V,
respectively,
assigned to trophic levels
were prepared from marine samples
taken in the Pacific off Oregon during 1961-1962.
These organisms had
been exposed in their natural environment to both fission products from
fallout and neutron-induced radionuclides from reactors on the Columbia
River.
Comparisons of spectra of organisms from different trophic levels,
determined from stomach contents and the
and Ce141
were concentrated by primary producers and
by carnivores.
ducers).-
vores.
literature,
herbivores,
but not
Cr51 was abundant in only filtered samples (primary pro-
Mn54, Co60, and Cs137
Zn65
show that Zrg5-Nb9S
were found in only herbivores and carni
was found in every marine organism examined.
that the abundance of Zr95-Nb95 and
in marine trophic level studies.
in
particular,
We conclude
may be useful
Peaks due to these fission products
are greatly reduced in spectra of predaceous animals, compared with
spectra of herbivores.
92
INTRODUCTION
The oceans receive a substantial share of radioactive fallout
resulting from nuclear testing because of their large areas and the
drainage they receive from the continents.
Prevailing westerly winds
carry tropospheric fallout from nuclear tests in northeastern Asia
across the Pacific Ocean to North America.
Levels in the environment
are normally quite low, but certain fission products are accumulated by
filter-feeding zooplankton (Osterberg, 1962b, 1963).
Radionuclides are also introduced by nuclear reactors at Hanford,
Washington.
Many trace elements in the Columbia River water used to cool
the reactors are activated by the intense neutron flux (Nelson, ed., 1961).
These induced radionuclides are returned to the river, and ultimately
portions of them enter the ocean.
The presence of radioisotopes in the ocean off the Oregon coast and
the supply of nekton and plankton available from our midwater trawl program have made it possible for us to investigate the presence of both
fallout and neutron-induced radionuclides in oceanic food chains.
The
gamma-ray spectra of marine organisms from different trophic levels are
compared to determine which radionuclides are passed through food chains,
and which are discriminated against.
Assignment of an organism to a
particular trophic level is, in most cases, based on studies of stomach
contents, supplemented by references from the literature.
METHODS
Phytoplankton and detritus were collected by passing surface sea
water through a 5-inch membrane filter (0.65 microns), plus glass fiber
93
pre-filter (Gelman Instrument Company).
The filters were ignited in an
open crucible to destroy the membrane filter, the residue placed in a
muffle furnace for an hour at 500°C and then ground with mortar and
pestle before packing into counting tubes.
Macroplankton and micronekton were collected in a 6-foot Isaacs.
Kidd midwater trawl towed for 30 minutes from 200 m depth to the surface.
Plankton and nekton samples were freeze-dried after formaldehyde preservation.
Large or oily samples were further concentrated by aching
in a muffle furnace.
Dried and/or ashed concentrates of the entire
animalsl/ including digestive tracts were then packed into counting tubes
1/ Salps and, of course, tuna liver were exceptions.
Only the opaque
interior "nucleus" (or digestive tract) of the salp was used, since the
transparent outer portion was found to be low in radioactivity (Osterberg,
et al.,
1963).
(Falcon Plastics, Item #2001).. Tubes, containing the prepared samples were
placed in the well of the 5" x 5" NaI(TI) primary crystal of the Hanford,
Washington, total absorption anticoincidence spectrometer (Perkins, et al.,
1960) for analysis.
Counting time was 30 minutes, with 30-minute back-
ground subtracted.
RESULTS
Trophic Level Relationships
The first trophic level in the pelagic environment consists of
single-celled plants.
feeding herbivores.
The second trophic level consists of filterCarnivores compose the higher trophic levels,
Most
94
food relationships are not simple food chains, but are more often complex
webs.
Since feeding animals are opportunists, the uncertainties of diet
are great, particularly in the case of large predators.
Nevertheless,
food patterns do exist and some division into trophic levels is possible.
Trophic Level I
Phytoplankton and detritus were trapped on a membrane filter through
which
surface sea water was
passed.
Most animals were removed by pre-
filtering through a #6 mesh net.
Trophic Level II
Euphausia pacifica.
Euphausiids may feed on phytoplankton, small
crustacea such as copepods, or detritus (Ponomareva, 1954; MacDonald,
1927; Marshall, 1954).
Although Ponomareva (1954) noted that E. pacifica
occasionally fed on crustacea, it is primarily a filter-feeding herbivore.
Setae of the thoracic legs of our adult E. pacifica are about 20-40-}
apart; thus, the filtration apparatus is equipped to collect most marine
diatoms.
Calanus cristatus, Salpa spp., and Clio pyramidata are pelagic zooplankton which feed on suspended particles, principally phytoplankton.
Calanus are mainly herbivores (Marshall and Orr, 1955), as are the
cavolinid pteropods (Marshall, 1954; Yonge, 1926).
Salpa spp. are in-
discriminate feeders and principally phytoplankton grazers (Marshall,
1954; Yount, 1958; Foxton, 1961).
95
Trophic Level III
This carid prawn is particularly common near
Pasiphaea pacifica.
the mouth of the Columbia River.
Stomachs of 31 individuals were examined.
Contents consisted of fragments of animals which were apparently dismembered and masticated before ingestion.
Chitinous remains of crustacea
were noted, including mandibles and eyes similar to those of Euphausia
ifica.
Several cephalopod beaks were also found.
These observations,
like those on other oceanic prawns (Chace, 1940), indicate that adult P.
pacifica are carnivores.
Only a few observations on the feeding habits
Sergestes similis.
of this mesopelagic prawn have been made
previously (Barham, 1956).
Our
examination of the stomachs of these common animals revealed them capable
of ingesting whole zooplankton.
Entire'copepods were noted as well as
fragments of larger euphausiids and prawns.
Several fish scales were
also present.
Lampanyctus leucopsarus.
Thirty-four stomachs of this lantern fish,
the dominant mesopelagic fish taken in midwater trawl collections off
Oregon, were examined.
It feeds largely on euphausiids,
calanoid copepods,
and amphipods.
Tactostoma macropus.
fish were examined.
Stomachs of 52 specimens of ,this stomiatoid
Many were empty.
Euphausiids and sergestid prawns
occurred most frequently, but about half the total stomach contents by
volume was due to the presence of several lantern fish.
T. macropus
appears to be intermediate between trophic level III and IV.
96
Trophic Level III-V
Thunnus alalunga.
Several hundred migratory albacore tuna were
captured during the summer of 1962, from 25 to 50 miles off the northern
Oregon coast, and stomachs of 62 of the tuna were examined.
empty or less than one-quarter full.
Most were
Cephalopods composed about 75
percent of the bulk of the stomach contents, fish about 18 percent, and
crustacea about 5 percent.
Radioanalyses
Gamma-ray spectra of organisms from several trophic levels taken
at the same time and location are shown in Figure 1.
Trophic level I is
represented by a membrane filter through which surface sea water has been
passed.
Although chlorophyll a was present (1.56 mg/m3), the data do not
indicate the percentage of particulate organic matter.
The low amount of
potassium-40 suggests that only a small quantity of inorganic material
(probably as clay particles) was present.
The K40 level on this filter
was nevertheless higher than in filter samples from further offshore.
Cerium-141, ruthenium-103, and zirconium-95 - niobium-95,2/ which are
2/ Our figures generally show the peak due to Zr95-Nb95 simply as
but the techniques used do not permit a separation of Zr95 from its
daughter, Nb95.
106
There is also some uncertainty with regard to Ru103 and
but our evidence indicates a preponderance of Ru103 in these samples.
No attempt was made to differentiate between Ce141 and
particulate in sea water (Greendale and Ballou, 1954), were trapped by
the filter, whereas zinc-65, which is ionic in sea water, was low even
500
TROPHIC LEVEL I
400
Cr51
200
Membrane filter
I
300
Z r95 - Nb95
Ce141
100
K40
0
1500
1400
TROPHIC LEVEL II+
1300
TROPHIC LEVEL III+
Lampanyctus leucopsarus
TROPHIC LEVEL M+
Pasiphaea pacifica
50
CHANNELS
Figure 1.
Comparison of gamma emitters from several trophic levels.
Organisms for all four spectra were collected 15 miles off
Astoria on 5-6 April 1962. All trophic level II and III
animals were from the same trawl sample.
97
though abundant in waters near the mouth of the Columbia
River
(Osterberg,
Zn65 ions bound to particles would appear on the
1962a).
Only those
filter.
The chemistry of chromium in sea water is uncertain, but the
abundance of Cr51 (from Hanford) on filter samples (Fig. 1) indicates
that a fair portion is either particulate or associated with particles.
At trophic level II, represented by Euphausia pacifica (Fig. 1),
two striking changes in the gamma spectrum are observed:
lower Cr51, and higher
Zr95-Nb95
Zn65
than on the filter.
relatively
Ru103,
The
and
peaks indicate that either the particulate radionuclides are
picked up directly
filter-feeding euphausiids while feeding or they
by
may adsorb to larger
particles, which are eaten.
Concentration of these
radionuclides does not appear to be due to adsorption on the surface of
the zooplankton, however (Osterberg, et al., 1963).
The
Cr51 particles
are either too small to be filtered out by the setae of the euphausiid
or are selectively discriminated against, although in some cases small
amounts of Cr51 are found in euphausiids.
The lantern fish, L. leucopsarus, represents trophic level III.
Cerium-141 and
Zr95-Nb
95
are discriminated against-compared with the
preceding trophic level (Fig. 1), even though E. pacifica was abundant
in the stomachs of the fish, but
Zn65
is still present.
The spectrum
of the carid prawn Pasiphaea pacifica (Fig. 1) closely resembles that
of the lantern fish, reinforcing the conclusion from stomach analyses
that both the prawn and the lantern fish are principally carnivores.
Zn65
was the most conspicuous gamma emitter in the spectra of both
animals.
98
Albacore tuna, taken 30 miles off Astoria, 10 August 1962, represented the highest trophic level examined (III-V).
The spectrum of a
single ashed sample of tuna liver indicated the virtual absence of particulate fission products, with the possible exception of Ru103
Concen-
tration of Zn65 was exceedingly high compared with other peaks of the
spectrum.
A preference for other cations was also shown, with peaks due
to cobalt-60, potassium-40, manganese-54, and cesium-137.
DISCUSSION
Spectra in Figure 1 show only the relative abundance of the different
isotopes,
and cannot be compared quantitatively, since no allowance has
been made for sample size, radioactive decay, and efficiency factors.
However, normalization of the data to obtain absolute concentrations of
the various isotopes indicates that the relative spectra demonstrate real
trends (Fig. 2).
E. pacifica often contributes the greatest biomass in our trawl collections.
samples.
Its abundance permitted radioanalyses of about 150 euphausiid
The year-round availability of this macroplankter and its
affinity for radionuclides make it a useful biological standard with which
to compare other organisms.
Since environmental radioactivity varies with
location3/, comparisons ideally should be restricted to organisms taken at
3/ Short period variations in fission product levels in euphausiids from
a single location are small. Nine consecutive tows, made over a period
of 8 hours, 50 miles off Newport, 11-12 April 1962, show the following
averages and standard deviations: Zr95-Nb95, 13.6 1:1.2 picocuries/gram
141
17.5 T 2.8 pc/g, dry weight.
and
Filter per liter
Euphausia pacifica
Lampanyctus leucopsarus
Pasiphaea paci f i ca
K 40
Zn65
Zr- Nb95
`
Ru'03
Cry'
Ce&4t
0
Figure
2.
5
20
PICOCURIES / GRAM WET WEIGHT
10
15
25
All organisms were
Concentrations of gamma emitters from several trophic levels.
collected 15 miles off Astoria on 5-6 April 1962.
Note different units for filter
sample.
99
the same time and
sample.
place.
Our comparisons were usually from the same trawl
They show that certain
copepods,
salps, and pteropods also con-
With euphausiids, these animals represent
centrate Zr95-Nb95 and
the bulk of oceanic herbivores in our trawl samples.
Similarities in the spectra of two animals from trophic level II
are seen in Figure 3.
herbivores.
These spectra are somewhat typical of our oceanic
That is, prominent peaks due to Zr95-Nb95 and Ce141 appear
in the spectra of salp, copepod, pteropod and euphausiid samples taken
in late 1961 and throughout 1962.
When spectra of organisms from higher trophic levels are compared
with the spectrum of E.
form a general pattern.
pacifica,
the details described for Figure 1
That is, in every case there was a reduction in
the Zr95-Nb95 and Ce141 peaks in predators relative to those observed in
euphausiids.
This discrimination was noted in the dozen or so instances
when direct comparisons from the same sample were
forced by a large number of analyses
possible,
of high trophic
isms that invariably were low in fallout peaks.
and was rein-
level marine organ-
This experience prompted
us to consider Sergestes similis a predator on the basis of its spectrum,
which shows a marked reduction in fission products compared with that of
E. pacifica (Fig. 4).
Subsequent stomach analyses verified this predic-
tion.
Ruthenium-103, presumably an anion (Lowman,
1960),
was the only
obvious non-cationic species regularly found in trophic levels III-V.
It was present in the tuna
a cotton rat (Sigmodon
liver,
hispidus)
and has been reported in-the liver of
(Kaye and Dunaway, 1962), although
Chipman (1960) observed little uptake of Ru106 from digestive tracts of
100
menhaden (Brevoortia tyrannus).
Cesium-137, which we also found in tuna
liver, has been observed to concentrate slowly in some marine fish (Chipman,
1958; Baptist and Price, 1962). Pendleton and Hanson (1958) show that
Cs137 is particularly
concentrated
at higher trophic levels.
The affinity for zinc by all trophic levels, with the possible
exception of trophic level I, makes Zn65 by itself a poor indicator of
feeding relationships.
We have found Zn65 in the predaceous squid
(Onychoteuthis banksi) in surface waters, and in sea pens (Pennatulacea)
attached to the bottom at 700 fathoms.
This ubiquity of Zn
65
makes it
of singular interest.
The prominence of Zn65 in marine organisms has been mentioned by
Lowman (1960), who stated that zinc and other transition elements were
concentrated while cesium and strontium were discriminated against in
marine animals, this situation being reversed on land.
Zn65 is a prom-
inent isotope in fresh-water fish from the Columbia River (Davis, 1958).
Joyner (1962) found that carnivorous, marine, lagoon fish concentrate
Zn65 to a greater extent than do herbivores.
However, the levels of
Zn65 reported in oysters (Watson, et al., 1961) near the Oregon-Washington
coast were much higher than we found in any oceanic planktonic or nektonic
organisms from the same general area, indicating that trophic level itself
is not the sole criterion of ability to concentrate Zn65
CONCLUSIONS
The presence of the Hanford reactors on the Columbia River makes
Zn65 the most common gamma emitter in marine
coastal waters.
organisms from the Oregon
All marine animals examined had accumulated this isotope.
Zr95
Ce141
140
120
TROPHIC LEVEL ]I+
100 L
Euphausia pacifica
80
Zn65
60
40
K40
I
z
D
o
U
20
A
0
Zr95
J
70
I
I- 60 L Ce141
0
TROPHIC LEVEL II+
50
I
Calanus cristatus
40
30
Zn65
K40
20
10
0
0
100
50
CHANNELS
Figure 3.
Comparison of spectra of euphausiids and copepods from the same
miles off Astoria on 6 June 1962.
sample, collected 105
The scatter in the lower spectrum is due to small
sample size.
Zr95
600
TROPHIC LEVEL II+
500
400
Zn65
Ce 141
300
1
200
F-
z
Euphausia pacifica
Ru 103
100
M
0
0
0
Zn 65
TROPH 1 C LEVEL l+
Sergestes simitis
Ce141
0
Ru 103
Zr95
50
100
CHANNELS
Figure. 4.
Comparison of spectra of euphausiids and sergestids from the same sample, collected 25
miles off Newport on 6 November 1961.
101
Cr51, from the same source, was abundant only
in filter samples repre-
senting the first trophic level, and was not common at the higher trophic
levels.
The presence of particulate fission products Zr95-Nb95 and Ce
appears to be a good criterion for distinguishing whether an animal is
Rarely are these radioisotopes prominent in
herbivorous or carnivorous.
the spectra of predaceous animals in the sea, and then only in small
amounts as compared to the same isotopes in marine herbivorous animals
collected simultaneously.
The highest trophic levels in the ocean, as
evidenced by our tuna sample, almost completely discriminate against
particulate fission products, but concentrate cations.
Despite the
chemical competition from potassium, which is abundant in sea water,
Cs137
was present in tuna liver and in a carid prawn, both representa-
tives of higher trophic levels.
Radioactivity in the marine environment varies greatly with time
and location.
Very likely changes in stable trace elements also occur,
although comparable data do not exist.
Future work on marine food chains
should include both measurements, so that specific activities can be
determined.
However, these local differences are minimized in our data
by intercomparing organisms from the same trawl sample.
We conclude that particulate radioactive fallout will be concen-
trated at the second trophic level by filter-feeding plankton, but very
little of this radioactivity will be present in the animals commonly
utilized in the diet of man.
On the other hand, neutron-induced
Zn65
is more likely to enter the human food chain, but is one of the more
innocuous radioisotopes, since it decays principally by electron capture
and few ionizing particles are emitted.
The discrimination against
102
particulate fission products tends to make the higher trophic levels of
the marine food chain excellent sources of food in the event of high
levels of radioactive fallout.
ACKNOWLEDGMENTS
We thank R. W. Perkins of General Electric's Hanford Laboratories
for making his equipment available to
us,
and for his
assistance with
certain technical aspects of the gamma-ray spectrometry.
This research was carried out under grants
1726
AT(45-1)1750 and AT(45-1)
with the Atomic Energy Commission, Nonr 1286(02) with the Office of
Naval Research, and Grant G 23103 with the National Science Foundation.
103
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1958.
Distribution and ecologic aspects of Central
Pacific Salpidae (Tunicata).
Pacific Sci., 12:111-130.
107
ZINC-65 IN EUPHAUSIIDS AS RELATED TO COLUMBIA RIVER
WATER OFF THE OREGON COAST
Charles Osterberg, June Pattullo and William Pearcy
Abstract
Most of the zinc-65 in the northeast Pacific Ocean originates in the
Columbia
River as a
operations.
in the
result of the Hanford, Washington, nuclear reactor
The Columbia River is also the principal source of fresh water
region, so that at
able far at sea because
fate of the
river
certain seasons
the plume of the river is detect-
of its low salinity.
water at
In an effort to determine the
sea, euphausiids from the ocean off Oregon were
used as biological monitors.
The Zn65 content of the euphausiids was
measured by gamma-ray spectrometry, and the relationship between Zn65 content and the salinity distribution over the area was examined.
Some correla-
tions were apparent, although seasonal changes of Zn65 content in euphausiids
were not
great.
Zn65 levels
remained fairly high off Oregon even when
Columbia River water was not evident as a low salinity plume.
This indicates
that water from the Columbia River, which accumulates as a plume off Oregon
in the summer, influences the Zn65 content in animals in the area throughout
the year.
The long half-life of
Zn65
in the mixed
layer,
the diurnal migra-
tions of euphausiids, and the seasonal reversal of currents all may contrib-
ute to the maintenance of this reservoir of
coast.
Zn65
in the ocean off the Oregon
108
INTRODUCTION
The outflow of the Columbia River dilutes the salinity of the surface water in certain sections of the, northeast Pacific Ocean,. forming a
shallow lens of low salinity water which over-rides the more dense oceanic
water.
This lens of water is known as the plume of the Columbia River,
and, by definition, consists of water having a salinity of 32.5 0/00 or
less.
In summer, prevailing winds and currents carry this less saline,
water southward, sometimes forming a pool approximately 100,000 square
miles in area off the Oregon-California coast.
In winter, surface waters
are mixed to a greater depth, and Columbia outflow is diminished, while
coastal rivers attain maximum flow.
At this time the plume becomes smaller
and less distinct and appears to be driven northward by the prevailing
winds (Barnes et al. 1957; Anderson et al. 1961, 1962; Budinger et al.
1963).
Water from the Columbia River is used to cool the nuclear reactors at
Hanford, Washington.
The intense neutron flux in the reactors activates
certain trace elements in the coolant water.
Stable zinc-64, for example,
captures a neutron to become radioactive zinc-65.
An estimated 38 curies
per day of Zn65 passes Vancouver, Washington, en route to the sea.
This
rate of replenishment and the 245-day half-life of Zn65 lead to an equilibrium value of 14,000 curies of this isotope in the Pacific Ocean as a result
of Hanford activities (Nelson ed. 1961).
Zinc-65 has been found in sessile organisms along the Oregon-Washington
coasts (Watson et al. 1961), in marine plankton at some distance from shore
(Osterberg 1962, 1963), and in marine sediments near the Columbia River
(Osterberg et al. 1963B).
Zinc-65 in sea water is more difficult to detect
because of the low concentrations that exist.
It is the affinity of marine
109
organisms for zinc that makes them useful monitors of
Zn65
The constant low-level radioactivity in the Columbia River and the
inherent sensitivity of radiotracer techniques invite an attempt to
trace river water at sea by using marine animals which concentrate Zn65
to readily measurable levels.
If Zn65 is a characteristic unique to
Columbia River water, and if marine organisms accurately reflect the
radioactivity of their environment, then Zn65 in animals should be a
good indicator of the presence of Columbia River water.
This hypothesis
is explored, using Euphausa pacifica as a monitor of Zn65.
Zinc-65 con-
centration in this abundant macroplankter is correlated with salinity
distribution in an effort to delineate the seasonal distribution of
Columbia River water in the ocean.
METHODS
Euphausiids were collected by using a six-foot Isaacs-Kidd midwater
trawl at three east-west series of stations extending 5 to 165 nautical
miles offshore from the Columbia River (Astoria), Newport, and Coos Bay.
In one case, an additional series was made off Brookings, Oregon.
Oblique
tows from 200 meters to the surface, averaging 30 minutes duration, were
made at night.
The bulk of the samples usually consisted of euphausiids, with
Euphausia pacifica predominating.
Of the 194 midwater trawl collections
throughout the period of study, 132 contained sufficient E. pacifica for
radioanalysis (i.e., at least 40 g. wet weight).
E. pacifica were separated from the preserved samples, freeze dried,
and ground with mortar and pestle.
Approximately 13 cc of the sample were
110
packed into 15 cc plastic spectrometer counting tubes, corked and sealed
Samples were counted using General Electric's total absorp-
with paraffin.
tion anticoincidence spectrometer (see Perkins et al. 1960) at Hanford
Laboratories, Washington.
Data reduction
Counting time was 30 minutes.
and statistical analyses were made using an IBM 1620 computer.
Filter samples from rivers were obtained with 5-inch diameter membrane filters (0.65 micron) and glass prefilters (Gelman Instrument Co.).
Two filter units from each site were packed into each 15 cc counting tube.
Samples (500 ml) of the cation exchange resins, which were used with river
water, were counted in the well of a 9-inch crystal (Perkins 1961).
Variability of Zn65 in Euphausiids
Euphausiids concentrate
Zn65
(Osterberg
paring seasonal or geographic variations of
short-term variability of
Zn65
1962).
Zn65,
However,
before com-
some knowledge of the
in E. pacifica is desirable.
Euphausiids
were taken in a series of nine repeated tows over a 16-hour period at a
station 50 miles off Newport, 11-12 April 1962.
The mean radiozinc content
was 11.0 picocuries/gram dry weight, with a standard deviation of 1.5 pc/g.
This indicates a fairly consistent concentration of
Zn65,
and variations
which are small compared to seasonal or geographic trends.
The Columbia River as a Source of
Before the
Zn65
Zn65
content of E, pacifica can be considered indicative
of Columbia River water, it must be shown that fall-out
comparatively insignificant amounts in this region.
Zn65
occurs in
Although Zn65
is not
a fission product, it is associated with nuclear testing (Lowman 1960).
111
To check for Zn65 in euphausiids from areas relatively free from the effects
of the Columbia River water, euphausiids found off Alaska and off San Diego
Results show that a low-
and Los Angeles, California, were analyzed.!/
The existence
level background of Zn65 from fall-out does appear to exist.
of a widespread background
sence in
of Zn65 has been further confirmed by its pre-
a variety of foods in the eastern United States (Murthy et al.
1959), in fish and prawns in India (Chhabra and Hukkoo 1962), and in polar
cod (Boreogadus saida) from Arctic waters (Osterberg and McCauley lab notes
However, the quantity of
Zn65 normally occurring off Oregon
far exceeds
that found in other areas of the world, except near nuclear testing sites.
Additional evidence on the relative lack of fall-out
Zn65
is furnished
by comparisons of the radioactivity in the Columbia and Willamette Rivers,
which join near
Portland.
late matter filtered
detectable
Fission products were present in the particu
from the waters
of both
rivers,
only in the Columbia River (Fig. 1).
but
Zn65
was readily
There is a possibility
that fall-out Zn65 might be in a form chemically different from the radiozinc induced in the Columbia River.
Therefore, filtrates from both rivers
were passed through cation exchange columns (Dowex-50) to remove Zn
solution in the water.
in
This experiment also showed that the Zn65 peak
was prominent only in the spectrum of Columbia River water.
Since the
Willamette River (and all of the other Oregon rivers that we have sampled-2/)
is relatively free from
Zn65,
we conclude that most of this isotope found
in the Oregon coastal region was produced
at Hanford.
This situation is
1/ We thank Frank Hebard, U.S. Fish-and Wildlife Service, for the Alaska
sample, and Edward Brinton, Scripps Institution of Oceanography, for
those collected off California.
2/ Nehalem, Nestucca, Siletz, Suislaw, Umpqua, Marys, N. Santiam, S. Santiam,
Yamhill, Clackamas, Deschutes, Malheur, Owyhee, Burnt, Snake, John Day,
Metolius, Rogue, Coquille, Alsea, and McKenzie Rivers.
112
subject to
change,
however, since each nuclear detonation is a passible new
source of fallout
RESULTS
If
Zn65
in Euphausiids and Related Salinity Distributions
Zn65
in euphausiids reflects
water at
is
sea,
expected.
the distribution of Columbia River
then a negative correlation
between Zn65 and surface salinity
Figures 2-6 show amounts of
Zn65
in euphausiids and salinity
distributions at approximately the time when the euphausiids were collected.
During July-August 1961 (Fig.
2),
siids from Newport than in the sample from
Columbia River.
was more abundant in euphau-
Zn65
Astoria, at the mouth of the
Lower values, but relatively uniform with distance from
shore, were found in euphausiids taken off Coos Bay.
The salinity data,
taken a month earlier, indicate a tongue of relatively fresh surface water
extending at least as far south as the California border (salinity 32.5
0
/oo).
This shallow lens of water is the plume of the Columbia River
(Anderson et al.
1962,
Budinger et al. 1963).
During November 1961 (Fig.
3),
low Zn65 values were found everywhere
except at the station nearest the mouth of the Columbia River.
from this station the
addition,
the south.
(1962),
Zn65
Seaward
content of euphausiids decreased markedly.
close to shore there was a gradual decrease in radioactivity to
Again, our salinity data, as well as those of Anderson et al.
indicate that the Columbia River plume extended south of Coos Bay.
Figure 4 shows that in January Zn 65 was still present in appreciable
quantities in euphausiids taken off
Newport,
but values at stations off
Coos Bay, particularly near shore, were lower than in
November.
The low
I Cr51
4000
COLUMBIA RIVER
( Corbett - Jan. 10, 1963)
3000
Zn65
C e 141
1
2000
1
Z r95
Mn54-56
A
1000
C S 137
Ru103
l
)
K 40
SC 46
i
I
F-
i
WILLAMETTE RIVER
Ce 141
( Buena Vista Ferry
3000
-
Jan. 10, 1963)
Zr 95
2000
Zn65
1000
1
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
CHANNELS
Figure 1.
Gamma-ray spectra of particulate material in two Oregon rivers.
Note chromium-51 and zinc-65 peaks in the Columbia River spectrum.
BROOKINGS
Figure 2.
Zinc-65 in euphausiids (bars) and salinity distribution (contours) during summer, 1961
(see text for dates). Numbers above bars indicate picocuries per gram dry weight of
euphausiids. All stations where euphausiids were collected are indicated by bars or
dots. Dots show stations where euphausiids were insufficient for radioanalyses. In
no case where analysis was possible was Zn65 absent.
47
X05
\45
125
\65
DEPTH
50
IN
100
METERS
150
COOS BAY
SALT N ITY
28
30%.
32.5%°
Figure 3.
Same as Figure 2 for November 1961.
13
ASTORIA
17
0
DEPTH
N
50
100
METERS
200
COOS BAY
SALINITY
<
Figure 4.
28 %o
Same as Figure 2 for January 1962.
113
salinity of this inshore water was undoubtedly due to increased winter
runoff from the nearby Umpqua and Coos Rivers, rather than to the Columbia
plume.
Zinc-65 values at the four stations nearest shore off Coos Bay may
also have been reduced by admixture of water from the south (Davidson
Current) which occurs frequently in this area at this season, whereas,
water further offshore continues to flow from the north (H. 0. Publ. 570
1947; Sverdrup et al. 1942; Anderson et al. 1962).
Anderson et al.
(1962) point out that prevailing winds in winter
probably carry the Columbia plume northward.
However, low salinity and
relatively high Zn65 values off Newport during January indicated the
continued influence of plume water in this area.
euphausiids from 125 miles
On the other hand,
off,Astoria contained little Zn65, although low
salinity water was present there,
We believe that this low salinity water
off Astoria was not from the Columbia River, but instead was part of the
general low-salinity belt (modified Sub-Arctic Water) extending to the
Gulf of Alaska (Anderson et al. 1961).
This conclusion is based both on
the low Zn65 value and on the fact that winds that would drive the plume
westward are absent.
Exceptionally high values of
Zn65
were found during
very near the mouth of the Columbia River (Fig. 5).
March-April 1962
These high Zn
65
values occurred at a time when the plume was "pooled" close to the mouth
of the river by several months of strong winds from the south-west
(Anderson et al. 1962).
High radioactivity off Newport seems to be assoc-
iated with water fresher than 32.5 0/0o in spite of the fact that the
Columbia River plume is not thought to extend this far south during the
spring (Anderson et al. 1962).
114
Figure
Zn65
(July-August
6
1962)
represents the same season as Figure
was again lower off Astoria than off Newport or, during this year,
even Coos Bay.
Relatively high values of Zn65 in euphausiids were found
off Brookings in the tongue of fresher water offshore, which again seems
to be part of the Columbia River plume.
Much lower Zn65 values were found
in the four stations nearest the coast where the salinity was almost 34
0/oo (undoubtedly due to upwelling).
In summary, the maximum value of Zn65 in E. pacifica, was found off
the mouth of the Columbia River in spring, 1962, (Fig. 5).
However, large
amounts were found off the central coast of Oregon throughout the year.
In summer, these high values were from euphausiids taken in the area of
the Columbia River plume, as indicated by salinity measurements.
It is
surprising that values of Zn 65 were sometimes. higher off central Oregon
than off the mouth of the Columbia River (Fig. 2, 4, and 6)
Moreover,
relatively high concentrations were found off southern Oregon as much as
250 miles from the Columbia (Fig. 6).
find that seasonal variations in the
It was particularly unexpected to
Zn65
in euphausiids were not great,
and that comparatively high values were found off Oregon in the winter,
when the plume presumably extends northward and is absent off the Oregon
Coast.
Zn65
as an Indicator of Columbia River Water
In the absence of fallout Zn65, the Zn65 which we measured in euphau-
siids must be derived from Hanford
water.
activities,
i.e., the Columbia River
In interpreting the distributions of euphausiids
containing Zn65
and the disparity between this and the location of the Columbia River
136
COOS BAY
E
30%
32.5 %
Figure 5.
Same as Figure 2 for March-April 1962.
BROOKINGE
M,
Figure 6.
Same as Figure 2 for July-August 1962.
115
plume, we consider the following physical and biological factors: (1)
variations in the amount of Zn65 introduced into the Columbia at Hanford,
(2) amounts of Zn65 reaching the ocean,
decay,
(3) losses at sea due to nuclear
(4) currents affecting the movement,of the plume,
currents and vertical migrations on transport
Zn65 in the mixed layer, and (7)
f Zn 65,
uptake and retention
(5) effect of
(6) half-life of
of Zn65 by
euphausiids.
(1) Variations in the Amount of Zn65 Introduced into the Columbia at Hanford
The quantity of
but data are
by the
Zn65
entering the, Pacific Ocean undoubtedly varies,
not available on the variations in the amount of Zn65 released
reactors.
Recent reports indicate
that.
improved techniques have
reduced Zn65 output by about 25 percent (Schneller 1962), but the date of
this change was
Pacific Ocean
not'given.
for 1961
However, equilibrium values of Zn65 in the
(Nelson,
1962)
are unchanged from the previous year
(Nelson, 1961), which indicates that this reduction occurred after 1961.
Perhaps the lower values off Newport in the summer, of 1962 (Fig. 6), com-
pared with the summer of 1961 (Fig. 2), reflect this reduction.
(2) Amounts of Zn65 Reaching the Ocean
Because of the transitory nature of,Zn65, the amount which reaches
the ocean will be affected by the time it takes water to flow from Hanford
to the sea.
Dams on the Columbia, by increasing this time, allow more
decay and thus tend to reduce the output of Zn65 into the ocean.
Another
factor is uptake by the biota of the river (Davis and Foster, no date).
We have no quantitative estimates of these complex factors, but believe
their bearing on the problem of tracing the Columbia River is negligible
116
compared with other uncertainties.
(3) Losses at Sea Due to Nuclear Decay
If only physical
245 days.
decay is
considered, half of the Zn65 is lost in
However, steady state conditions
for Zn65 exist in the ocean
off Oregon in that decay is approximately balanced by replenishment of
Zn65 from the Hanford operations (Nelson 1961).
the river flows southward
in the ocean (as it appears
summer), decay will result in
time and distance.
But as the plume of
a gradual decrease
to do in the
in radioactivity with
If this were the only loss, the transit time of the
water could be computed by measuring the change in Zn65 concentration
in the water.
Let us assume for the moment that measurement of Zn65 in euphausiids
is equivalent to measurement of Zn65 in water,
The spatial and temporal
changes in Zn65 concentration in euphausiids off Astoria are very large.
Therefore, interpretation of this series of samples would be difficult.
However, Zn65 values for the Newport and Coos Bay series are less variable
and more confidence can be placed in averages.
The average of the Coos
Bay series was always lower than that of the Newport series.
If the
lower amounts of Zn65 at Coos Bay are attributed entirely to nuclear
decay as the water flows from north to south, the travel time ranged from
34 days in November 1961 to 309 days in summer 1961.
Anderson et al. (1961) state that "the current drift (of the southerlysetting California Current) as computed from the dynamic topography of
the sea surface is small, with average values of the order of 5 cm/sec
or less and maxima up to 20 cm/sec (10 miles per day) in the spring and
117
summer."
at these rates
Zn65 carried
by the southward. drift would cover
the distance between Newport and Coos Bay in about 8 to 40 days;'this is
considerably less than the times computed from the rate of physical decay
of Zn65
This leads us to conclude that, although radioactive decay is undoubtedly a factor effecting a decrease in Zn65 concentration as the
water flows from the latitude of Newport to that of Coos Bay, it cannot
be the only or even the most important factor.
(4) Currents Affecting the Movement of the Plume
The plume itself is a very shallow phenomenon and may be thought of
as a thin anticyclonic gyre embedded
surface currents.
Currents
generally southward
in
in the prevailing or "steering"
within 100
miles of, the Oregon coast are
summer, and, less consistently, northward in
winter (H. 0. Publ. 5,0 1947).
The outer edge of the plume generally
Most of these currents are weak
lies in the prevailing southward drift.,
with speeds of less than half a knot.
In addition to the general coastal
drift, offshore motion of the upper layers is present during summer when
upwelling occurs along the coast (Pattullo et al. in prep.).
Consider the behavior of a hypothetical plume that leaves the mouth
of the Columbia as a discrete discharge during the month of June.
It
would drift southward (at about 5 cm/sec at the core), and seaward, undoubtedly
spreading and becoming saltier with time.
Zinc-!65 concentration
in the plume would be diluted by mixing with salt water, but,, on'the
whole, would tend
to. remain near
would disappear as a result
the surface..
of turbulent
Eventually, the plume
mixing.
118
Although grossly oversimplified, this general pattern agrees with
the behavior of the plume as described by Anderson et al.
(1961, 1962).
The principal difference between the simplified "model" and the real
river plume is that the flow is not a single burst in June but has some
persistence during the summer months.
simply detach itself from the river
Therefore, the plume body does not
as a fixed
quantity of fresh water,
but increases in freshwater content, as well as in area, during the summer.
Winter mixing is such, however, that the plume completely loses identity
each year and can be considered an annually recurring event.
Occasionally
a secondary maximum in Columbia River flow is observed during winter.
This does not reinforce the old plume body off the Oregon coast, normally,
but is driven northward along the Washington
coast instead.
Surface drift is directly influenced, apparently, by winds.
summer the North Pacific high
pressure area
is well developed.
During
The
Oregon coast lies under the influence of the northwesterly winds at the
northeastern edge of the high.
During winter, this high retreats to the
southwest and the southeastern sector of the Aleutian low frequently
dominates the area; this leads to southerly winds.
However, at any
particular time the meteorological conditions may not conform to this
generalized pattern, and deviations from prevailing flow can be expected
to result.
During winter southwesterly winds result in a "pooling" of
river water along the shore adjacent to the mouth of the Columbia River
(Anderson et al. 1962).
is
the'area
At this season, river discharge is low and so
of the "pool" compared with the summertime pattern.
However,
the Zn65 content is high because of the high concentration of river water
in a restricted area.
119
65
(5) Effect of Currents and Vertical Migrations on the Transport of Zn
If all the Zn65 released by the Columbia River were retained entirely
within the plume, its study would involve only surface flow and transport.
Since euphausiids and other vertical migrants are found to concentrate
Zn65, however, we must consider the motions of the euphausiids and the
currents that affect them, as well as the currents which affect only the
plume.
Euphausia pacifica is known to make daily vertical migrations
(Esterly 1914, Tucker 1951, Barham 1956, Brinton 1962).
Off Oregon, E.
It is
pacifica is abundant in catches from the upper 200 m at night.
uncommon during the day, presumably descending into deeper water.
This
migration takes euphausiids well below the Columbia River plume water,
and, in fact below the temperature-salinity gradients that separate the
low density waters of the surface mixed layer from denser waters below.
Thus, biological transport of zinc across the pycnocline by such animals
as E. pacifica is undoubtedly more important than transport through this
layer by physical processes (see Ketchum and Bowen 1958).
Direct measurements of currents indicate that the pycnocline (at 100
to 200 m) is a region of velocity shear.
Recent data show that throughout
the year surface waters have had southward velocity relative to the deeper
waters (Pattullo et al. in prep.).
animals such as
Therefore, for vertically migrating
euphausiids, which reside
in deep waters
during the day,
the net drift to the south would be less than that of the plume.
an atom of
Zn65 in a euphausiid would move less rapidly out of the local
area than one floating freely in the plume, and concentration of
euphausiids
Hence
could
be expected to lag behind the plume body.
Zn65 in
120
Seasonal variations in subsurface currents also may affect euphausiid
distribution.
During wintertime, both subsurface (at least to 200 m) and
surface flow are probably slightly northward (Pattullo et al. in prep.).
This would tend to return to Oregon coastal areas euphausiids and Zn65
that had drifted southward during the summer.
Consequently, the patterns
of currents and vertical distributions of E. pacifica, both on a daily
and seasonal basis, appear to reduce the dispersion of Zn65 from the local
area off Oregon and may contribute to the absence of large seasonal vari-
ations of this radionuclide in
euphausiids.
The effects of vertical mi-
grations on the horizontal distributions of Antarctic euphausiids have
been described by Hardy and Gunther
(1935)
and Mackintosh (1937). They
also show that both daily and seasonal vertical migrations may affect the
retention of a population within a geographic area.
(6) Half-life of Zn 65 in the Mixed Layer
Budinger et al.(unpublished) report that mixing of the plume with
salt water occurs in such a way that radionuclides in the plume tend
to remain in the surface layers.
That is, salt water mixes vertically
upward into the overlying plume, while little fresh water is lost through
the resulting halocline.
Diffusion occurs along the outer edges of the
plume, and often "cells" of fresher water become separated from the plume
(Anderson et al. 1962).
Thus, radioactivity per unit volume of surface
water in the plume decreases with distance from the mouth of the river
even though little physical loss occurs vertically.
Zn65
Thus most of the
from the Columbia River is retained in the euphonic zone where it
readily enters into food chains.
121
Dilution of river water at sea makes measurement of Zn65 extremely
difficult,
except in marine
organisms,
of our non-biological measurements
which concentrate the zinc.
Most
therefore, been made in
near
have,
the Columbia estuary, where levels are much higher.
or,
There, Zn65 is found
in several conditions:
(1) as ionic zinc in the filtrate (concentrated
on cation and chelating
resins),
filtering
surface water
(2) attached to particles (collected. by
through membrane filters), and
(3) in organisms.
The concentration of ionic zinc is low and diminishes rapidly
seaward, so that it is not generally detectable by our techniques beyond
25 miles from
Zn65
the river's mouth (Osterberg and Cutshall lab notes)...
in or on particulate material can be detected farther at.sea.= -A small;..
but distinct Zn65 peak appeared in the spectrum of a filter through which
had been passed 109 liters of surface sea water from 45 miles off Astoria.
Zn65
in marine organisms remains easily detectable over the entire area
of our
with
observations,
organisms.
This indicates that much of the
Zn65
is associated
Major loss from the mixed layer therefore may be caused
by excretion and predation below the thermocline by. animals undertaking
diurnal migrations.
(7) Uptake and Retention of Zinc-65
The biological
it is
Euphausiids
half-life of Zn65 in
long, as it is in some marine
E. pacifica
is not known..
If
fish (Chipman et al. 1958), radio
zinc may be accumulated and retained for several months.
This would
help explain the small difference in Zn65 content between winter (when
the plume is not evident) and summer
present).
(when the plume is obviously
122
Zinc is a constituent of several enzyme systems (Vallee 1957)
and
marine organisms probably have a physiological need for it (Joyner 1962).
Metabolic demand for this
element,
which was the most common artificial
gamma emitter in marine animals off the Oregon coast (Osterberg et al, in
press),
may be greater during certain seasons of the year, or for certain
stages in the life history of euphausiids than at other
times.
Davis and
Foster (no date) show that fluctuations in the radioactivity of freshwater
minnows (Richardsonius
dependent.
balteatus),
for
were strongly temperature-
example,
They attribute the 75-fold increase in concentration of radio-
isotopes in the fish between winter and late summer to different metabolic
requirements,
due largely to temperature changes.
High Zn65 values near the mouth of the Columbia River in spring and
somewhat increased values in the fall correspond
fall plankton
E. pacifica grazes on
"blooms."
1954), from which
it appears to obtain
Zn65
roughly to
spring and
phytoplankton (Ponamereva
(Osterberg et al. 1963a).
Thus, a relationship is suggested between phytoplankton abundance and
increased
Zn65
content in
either to increased
growth of the
This relationship may be due
content per unit of phytoplankton during rapid
Zn65
population,
Foster and Davis
euphausiids.
or to increased grazing rates
(1955)
state
that
by the
euphausiids.
freshwater diatoms reach equilib-
rium with reactor effluent water in about an hour. Marine diatoms also
appear to concentrate radionuclides rapidly, since maximum
Zn65
values
are found in filter samples from nearest the mouth of the Columbia River
(Osterberg and Curl lab
notes).
Nevertheless, the highest
in euphausiids was generally found off
Newport,
Zn65
content
well to the south.
This
suggests that radioactivity of euphausiids is dependent on the time that
123
the animal has spent in water containing Zn65.
That is, a long period
is required for maximum concentration to be reached in the euphausiid.
In contrast, near the mouth of the Columbia River,
Zn65 content of
mussels (Mytilus spp.) was found to be generally higher than that of
euphausiids, but a similar comparison at Coos Bay showed less in mussels
(Watson et al. 1961).
The smaller gradient of Zn65 concentration in
euphausiids with distance is probably typical of plankton which drift
with the moving water.
On the other hand, the water surrounding sessile
organisms is continually renewed with changes of wind and tide..
CONCLUSIONS
Surface salinity patterns off the Oregon.coast change in,response
to the position of the Columbia River plume, which in turn is influenced
by a seasonal change in prevailing
winds. While Zn65
is shown to be
associated with the Columbia River, seasonal variations of
euphausiids are not
Zn65
in
marked, and the amount of Zn65 does not diminish
greatly in the absence of the plume in winter.
Vertical stability in
the ocean in this area (which generally precludes mixing-to great
depths),
seasonal current reversal and the migratory habits of euphau-
siids appear to maintain high levels of
the year.
Zn65
in euphausiids throughout
A long biological half-life of Zn65 would also help maintain
high Zn65 levels in the winter.
Maximum concentration of
Zn65
in euphausiids occurs close to the
mouth of the river in spring when the river's effluent is driven inshore
and "pooled"
by winds from the
higher off Newport, to the
southwest.
south,
Otherwise
levels.
are generally
perhaps due to a longer residence time
124
in plume waters and time lag in Zn65 incorporation.
Levels are lower.off
Coos Bay due to dilution and spreading of the plume and to decay of .
Two prominent local phenomena, the inshore wintertime current from the
south (Davidson Current) and summertime upwelling off Brookings, are both
reflected by lower Zn65 concentrations in euphausiids from those areas.
The great affinity of marine organisms for zinc and sensitivity of
modern gamma-ray spectrographic techniques make Zn65 in euphausiids easy
to measure.
Unfortunately, however, use of biological organisms as
monitors introduces many uncertainties.
The most important is that we
do not know how accurately the radioactivity of the euphausiid reflects
the radioactivity of his immediate environment.
This difficulty is com-
pounded if variations in stable zinc occur; local variations seem likely
because of the affinity of marine organisms for zinc.
However, no com-
parable data exist for stable zinc.
Another approach to the problem might be through the study of a
radioisotope that is not utilized extensively by marine organisms and
thus would be a more conservative indicator of plume waters.
Chromium-51
meets this requirement and furthermore is even more abundant in Columbia
River water than is Zn65 (Fig.
1)
(Nelson 1961).
However, this lack of
biological concentration of Cr51 makes it especially difficult to
measure, except near the mouth of the river before much dilution occurs.
Nevertheless, we are striving to improve our techniques so that radioactive elements in the Columbia River can become a more useful tool in
physical and biological studies of the plume and its effects in the
Oregon coastal region.
It is this low-level radioactivity which dis-
tinguishes the plume from other sources of fresh water in the area, and
seems to offer the most promise as a tracer of the river water at sea.
125
ACKNOWLEDGMENTS
We thank R. W. Perkins of General Electric's Hanford Laboratories
for allowing us to use his equipment, and for his assistance with certain technical aspects of the gamma-ray spectrometry.
to Harriet Van Arsdale,
We, are indebted
I. Lauren Larsen, Norman Cutshall, and the
captain and crew of the R/V ACONA for their work in the laboratory and
at sea.
We gratefully acknowledge the use of salinity data made avail-
able to us by Bruce Wyatt.
This research was carried out under grants AT(45-;1)1750 and
AT(45-1)1726 with the Atomic Energy Commission, Nonr 1286(02) with the
Office of Naval Research, and grant GP-622 with the National Science
Foundation,
126
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PUBLICATIONS AND PAPERS
Papers Published
Osterberg, Charles.
Fallout radionuclides in euphausiids.
1962.
Science
138:529-530. (With AT (45 -1)1750)
----- --
1962.
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Papers Accepted for Publication
Osterberg, Charles,
W. G. Pearcy and Herbert
Curl, Jr.
Radioactivity and
its relationship to oceanic food chains. J. Mar. Res.
AT(45-1)1750)
(With
See Section 6 of this report.
Papers Submitted for Publication
Osterberg, Charles, June Pattullo and William Pearcy.
Zinc-65 in
euphausiids as related to Columbia River water off the Oregon coast.
Limnol. Oceanogr.
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Pearcy, W. G.
Preliminary observations in the distribution of mesopelagic
fishes off Oregon.
J. Mar. Res.
(See Section 1 of this report.)
In Preparation
Pearcy, William G.
Species composition and distribution of pelagic
cephalopods from the Pacific Ocean off Oregon.
(See Section 2 of
this report.)
Pearcy, William G. and Charles Osterberg.
tion of
Zn65 and Zr95-Nb95
Notes on the vertical distribu-
from oceanic animals.
(With AT(45-1)1750)
See Section 5 of this report.
Pearcy, W. G.
Vertical distribution of numbers
and biomass of mesopelagic
fishes with an improved Isaacs-Kidd midwater trawl.
(See Section 4
of this report.)
Papers Delivered at Scientific Meetings
Pearcy, W. G.
Intermediate forage animals.
Northwest Pacific Oceanog-
raphers, Vancouver, B. C., February 19, 1962.
Pearcy, W. G.
Distribution of bathypelagic fishes over the continental
slope off Oregon.
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Corvallis, Oregon, August 28, 1962.
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