INVESTIGATION OF 'IHE ABUNDANCE AND RECRUITMENT
OF BOTTOMFISH OFF OREGON, WITH EMPHASIS ON DOVER SOLE
Public Law 88-309 Projects
ANNUAL REPORT
July 1, 1968-June 30, 1969
Prepared by:
Approved by:
.
Robert L. Demory, Project Biologist
Robert E Loef f e l , Marine Research Supervisor
U. S . Department of Interior
Fish and Wildlife Service
Bureau of Commercial Fisheries
Commercial Fisheries Research and Development Act
Subproject 1-4-R-4
Contract No. 14-17-0001-1906
August 1969
TABLE OF CONTENTS
Page No
..................................
PHASE PROGRESS..............................................
Market sampling..........................................
REPORTS AND PUBLICATIONS..
....................................
........................
........................................
..........................................
..............................
.......................
Year class strength ......................................
LITERATURE CITED. ...........................................
DOVER SOLE AGING STUDIES
Population dynamics of Dover sole
Fishing season
Fishing area
h t c h per unit of e f f o r t
Conversion of pounds t o numbers
.
LIST OF TABUS
Page No.
Table No.
1
2
Numbers of f i s h sampled by port, July 1, 1968, t o
June 27, 1969......
2
Conversion of pounds of Dover s o l e caught per hour
per s i g n i f i c a n t landing t o numbers caught per hour
per s i g n i f i c a n t landing i n area 3A.....
11
Age composition (per cent frequency) of Dover s o l e from
from PMFC area 3 A . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . .
13
Numbers of Dover s o l e caught by age group per hour
per s i g n i f i c a n t landing from area 3A................
15
Numbers of Dover sole, ages 7-13, caught per hour
per s i g n i f i c a n t landing from area 3A. Data arranged
by year c l a s s f o r year classes 1941-55. Data
taken from Table 4 . . . . . . . , . . . . . . . . . . . - . . . . . . . - . . . . , .
16
.................................
.............
3
4
5
LIST OF FIGURES
1
2
3
4
Age composition of Dover s o l e from PMFC areas 3A
(Astoria) and 28 (Coos Bay), May-September, 1966-68.
3
Age composition of English s v l e from PMFC area 3A,
1966-68..............................*.....-........
5
Age composition of p e t r a l e s o l e from PMFC a r e a 3A,
1966-68...........0............................-4...
6
Catch p e r e f f o r t of Dover s o l e from area 3A, MaySeptember. The horizontal l i n e i s the average
catch per hour per s i g n i f i c a n t landing
10
Dover s o l e year-class strength i n area 3A based
on measures of catch per e f f o r t f o r ages 7-13.......
17
..............
5
INVESTIGATION OF ?HE ABUNDANCE AND RECRUITMENT
OF BOTTOMFISH OFF OREGON, WITH EMPHASIS ON DOVER SOLE
ABSTRACT
Market sampling continues.
aging work i s current.
Aging s t r u c t u r e s have been read, and a l l
Age composition of Dover s o l e shows t h a t s t o c k s o f f Coos Bay a r e f u l l y
r e c r u i t e d 1-2 years l a t e r than stocks off the Columbia River. Age compos i t i o n of English s o l e reveals a very strong 1961 year c l a s s .
The aquarium experiment involving a study of Dover s o l e s c a l e growth
i n d i c a t e s t h a t s c a l e s of Dover s o l e a r e s e n s i t i v e i n d i c a t o r s of s t r e s s .
S t r e s s marks associated with handling t h e f i s h when s c a l e s a r e taken a r e
evident on nearly a l l f i s h .
Work on t h e population dynamics of Dover s o l e is accelerating. Yearc l a s s s t r e n g t h c a l c u l a t i o n s show t h a t year c l a s s e s of the e a r l y 1940's and
middle 1950's were stronger than normal.
REPORTS AND PUBLICATIONS
Three q u a r t e r l y progress r e p o r t s were prepared during the year.
Major
e f f o r t during t h e year was d i r e c t e d toward preparing two papers f o r publication.
The paper on aging Dover s o l e by s c a l e s underwent major revision.
A second paper on t h e depth d i s t r i b u t i o n of juvenile Dover s o l e a l s o under-
went revision.
Both manuscripts were submitted t o proper a u t h o r i t y within
t h e Fish Commission f o r editing.
A t h i r d s h o r t paper was w r i t t e n describing
the occurrence of some t a i l l e s s Dover s o l e .
A t a l k on t h e d i s t r i b u t i o n of juvenile Dover s o l e was presented t o t h e
Oregon chapter of t h e American F i s h e r i e s Society a t Corvallis i n January.
PHASE PROGRESS
A c t i v i t i e s during f i s c a l year 1968-69 were i n four main areas:
(1)
market sampling and t h e work-up of age data; (2) Dover s o l e aging studies;
(3) r e p o r t s and publications; and (4) population dynamics of Dover sole.
Market sampling
Market sampling f o r age and s i z e composition of Dover, English and
p e t r a l e s o l e and P a c i f i c ocean perch continued a t the l e v e l established i n
2
1966, i.e.,
400 Dover sole, 150 English sole, 200 p e t r a l e s o l e and 400
Pacific ocean perch per month.
These monthly quotas were seldom met
except during the favorable spring and summer f i s h i n g months.
With t h e
decrease i n perch fishing due t o depleted stocks few perch were sampled.
The numbers of f i s h sampled by p o r t a r e shown i n Table 1. Newport
and Coos Bay sampling is f o r the summer months only.
The aging s t r u c t u r e s
Pacific
collected from s o l e have been read, and a l l aging work is current.
ocean perch o t o l i t h s have been s e n t t o t h e federal-state aging u n i t a t
S e a t t l e f o r reading.
Table 1. Numbers of f i s h sampled by port, J u l y 1, 1968, t o
June 27, 1969
Port
Dover
sole
English
sole
Petrale
sole
Astoria
Newport
COOS Bay
2,800
100
1,400
1,614
473
354
1,831
490
Total
4,300
2,441
Pacific
ocean perch-
405
475
755
250
2,724
1,470
-
Age composition data of Dover s o l e have been collected a t Astoria
and Coos Bay since 1966.
Age composition of Dover s o l e stocks off the
southern coast (PMFC area 2E) is d i f f e r e n t than t h a t of stocks o f f the
northern Oregon-southern Washington coasts (PMFC area 3A).
For the
period 1966-68 males and females from area 3A a r e recruited t o the fishery
a t a younger age than they a r e i n area 2B.
Males a r e a l l y recruited a t
age 8 and 9 i n area 3A and a t age 10 i n area 23.
Females i n area 3A a r e
f u l l y recruited a t age 8 but a t age 10 and 11 i n area 28 (Figure 11.
Age samples of English s o l e have been taken since 1966.
With 3 years
of data available, it is now possible t o show something of the age s t r u c t u r e
of English s o l e from area 3A.
The 1961 year c l a s s s t i l l dominates the
5
10
Age i n years
15
5
10
15
Age in years
Figure 1. Age composition of Dover sole from PMFC areas 3A (Astoria) and
2B (Coos Bay), May-September, 1966-68
4.
catch since they were detected as 5-year f i s h i n 1966 (Figure 23.
data from area 2B show similar r e s u l t s .
Limited
There is a marked difference i n
the age composition of male and female English sole.
Males a r e 50% mature
Because of t h e i r
a t 22 cm (Harry, 1959) and a r e l e s s l i k e l y t o capture.
slower growth r a t e they remain i n the fishery several years more.
From
1966-68 males comprised only 13% of English s o l e landings from area 3A.
Even a t older age few males reach a desirable market s i z e .
Females a r e 50%
mature a t 31 cm which corresponds t o an age of about 3.5 years.
The p i c t u r e of English s o l e year-class strength w i l l be broadened i n
the near future when length-frequency d a t a from 1959-65 a r e dissected i n t o
constituent age groups by age-length keys.
Although p e t r a l e s o l e age composition d a t a a r e available from 1966
t o present, l i t t l e can be discussed a t t h i s time.
!dales and females a r e
f i l l y recruited t o the fishery by age 7 o r 8 (Figure 3).
Females
a r e longer lived than males and thus remain i n the f i s h e r y a longer time,
Females of the 1960 year class, first showing as age 6 i n 1966, were
dominant i n 1967 and 1968 age samples.
DOVER SOLE AGING STUDIES
In 1967 a two-pronged study was s t a r t e d on trying t o resolve d i s crepancies between s c a l e readings of tagged Dover s o l e and t h e length of
time a t l i b e r t y .
W sea-water aquarium of 150-gallon
purchased and s t ~ c k e dwith juvenile Dover sole.
capacity was
These f i s h were tagged
with Petersen discs f o r individual i d e n t i t y and a s c a l e collection procedure was established.
The second attack was t o t a g a number of Dover
s o l e a t sea, a t which t i m s scales were taken s o t h a t d i r e c t comparisons
could be made upon recapture.
Age ir. years
Figure 2.
Age compositi~nof English sole
PMFC area 3A, 1966-68
n MM~I~S
Females
Age
in years
Figure 3. Age composition of petrale sole from P W C area 3A, 1966-68
7.
The aquarium experiment is s t i l l underway.
Scales have been taken
monthly (except April 1968) since the experiment s t a r t e d i n February 1968.
Eight of the 12 f i s h i n t h e experiment a r e s t i l l living.
been l o s t since April 1969 because of disease.
Four f i s h have
This was due i n p a r t t o
nearly si~rrultaneousf a i l u r e of the pump and r e f r i g e r a t i n g u n i t .
This experiment has yielded tangible r e s u l t s .
I t was noticed on
scales of c e r t a i n f i s h t h a t a mark, termed a s t r e s s mark, was present
and apparently caused by handling when scales were collected.
For
example,fish number 2 showed s t r e s s marks on s c a l e s collected i n May,
June and August t h a t corresponded with s c a l e collections made i n March
(no scales i n April), May and July,respectively.
The mark t h a t showed i n
the June sample, r e s u l t i n g from the May handling, s o resembled an annulus
t h a t had I not known the h i s t o r y of the f i s h , t h e mark would have been
called an annulus.
S t r e s s marks were not common t o a l l f i s h ; however, 8 of 12 f i s h
showed a t l e a s t one s t r e s s mark.
Fish number 2 was the only f i s h t o show
more than one s t r e s s mark.
Tagging cruises i n November 1967 and April 1968 resulted i n 1,494
f i s h being tagged.
1969.
Twenty-four f i s h have been recaptured as of June 16,
Of t h e 24 tags recovered 17 were with the f i s h .
of the 17 recovered f i s h ranged from 14 t o 557.
been a t l i b e r t y a year o r more.
aided s c a l e interpretation.
easily identifiable.
Days a t l i b e r t y
Four of these f i s h had
Thus f a r , the tagging experiment has not
'Ihe s c a l e patterns were c l e a r and annuli
However, since 75% of the f i s h tagged were of sub-
legal s i z e ( - 2 8 an) it w i l l probably be several years before r e a l l y
tangible r e s u l t s w i l l be obtained.
Population dynamics of Dover s o l e
This p a r t of the progress r e p o r t w i l l b r i e f l y discuss r e s u l t s of
analysis of p a s t d a t a c o l l e c t e d a t Astoria from PMFC a r e a 3 A s i n c e 1948.
The subject, by no means, is exhausted and much remains t o b e done i n
order t o c a l c u l a t e yield.
Fishing season.
Because of t h e migratory behavior of mature f i s h ,
i .e., moving offshore during t h e l a t e f a l l and winter months t o spawn, it
was necessary t o s e l e c t a standard f i s h i n g season.
Dover s o l e landings
occur mainly during t h e period of May through September.
In f a c t , f o r
t h e years 1959-67 t h e average catch during t h i s period was 80%of t h e
total.
I t i s during t h i s period t h a t most sampling occurs.
Accordingly
a standard f i s h i n g season of May through September w a s established.
Fishing area.
Since nearly a l l sample d a t a from 1948 t o t h e present
WeEcollected from landings of f i s h caught from t h e area between Cape
Falcon and Willapa Bay, it was a l s o necessary t o limit t h e f i s h i n g area.
Calculations of year c l a s s s t r e n g t h a r e based on t h e stocks inhabiting
t h i s area.
These stocks may o r may not be r e p r e s e n t a t i v e b u t t h e d a t a
l i m i t a t i o n s allow no o t h e r choice.
Catch per u n i t of e f f o r t .
u n i t of e f f o r t were t r i e d .
Three d i f f e r e n t measures of catch p e r
These were:
(1) a t t h e 0% threshold l e v e l ,
o r t h e t o t a l catch of Dover s o l e h a i l e d2lr e g a r d l e s s of t h e ver cent of
Dover s o l e caught by tow, (2) a t the 30% catch level, i .e.,
those t r i p s
i n which t h e catch was 30% o r more of Dwer s o l e , t h i s i s c a l l e d a
s i g n i f i c a n t l a n d i n g and (3) pounds caught per hour of trawling p e r
s i g n i f i c a n t landing.
-I /
A hait i s uisu&Z weight estimate byl species of the cnount o f f i s h
retained.
Catch pep significant Zanding as a measure of catch pep effort wm
estabZished in 1953 and extmpotated back to 1948.
9.
The best measure of catch per u n i t of e f f o r t would be pounds per
tow; however, t h i s type of d a t a is nonexistent p r i o r t o 1958.
Unless
h a i l s were made by tow, it i s impossible t o determine which tows were
made primarily f o r Dover s o l e and, conversely, on which tows Dover s o l e
was incidental.
Catch per e f f o r t a t the 0% threshold level was f a i r l y
constant between 250 and 350 pounds per hour but useless f o r showing
long-term fluctuations because of the short time period involved.
Catch per s i g n i f i c a n t landing provided a usable measure of catch
per e f f o r t but, since it was based on the e n t i r e catch of a t r i p ,
f a c t o r s l i k e weather and market conditions exerted considerable but
not readily measurable influence on catch p e r e f f o r t .
The advantage
was t h a t it included data back t o 1942.
The measure of catch per e f f o r t f i n a l l y chosen was catch per hour
per s i g n i f i c a n t landing.
This measure was chosen f o r two reasons:
it provided a measure of catch per e f f o r t over a longer period of time
than e f f o r t a t the 0% catch level (1948 t o present) and it eliminated
the two f a c t o r s t h a t influence t h e length of a t r i p .
Catch per e f f o r t shows a downward trend since 1948 {Figure 4).
Since 1948 catch per e f f o r t has ranged from 288-680 pounds per hour and
averaged li42 p u n d s per hour. Since 1956 catch per e f f o r t has been
average o r below average; however, more years of d a t a a r e necessary t o
e s t a b l i s h long-term trends.
The r e s u l t s shown may r e f l e c t a normal
occurrence.
Conversion of pounds t o numbers.
Table 2 shows the s t e p s necessary
t o convert pounds of f i s h caught per hour of trawling t o numbers of f i s h
caught per hour of trawling.
The procedure is as follows:
(1) convert
average length t o average weight f o r each sex by means of length-weight
Table 2.
Conversion of pounds of Dover s o l e caught per hour ? e r s i g n i f i c a n t landing t o numbers caught per hour
p e r s i g n i f i c a n t landing i n area 3A
Males
NO. i n Ave.
yew sample w t .
Females
Total No, i n Ave.
wt.
sample w t .
Total
wt.
Total w t .
of males Per cent Per cent
Catch p e r s i g n i f i c a n t landing
G females
males
females
Weight
Numbers
i n sample by wt.
by w t .
Total Males Females Males Females
formulae--,I / (2) multiply number of f i s h i n sample by average weight t o obtain
t o t a l weight f o r each sex; (3) combine weights and determine percentage
weight by sex; (4) multiply weight of f i s h caught per hour of trawling
by the percentage weight of each sex; and (5) divide weight of each sex
caught per hour by respective average weight t o get numbers of each sex
caught per hour of trawling.
The number of f i s h by sex caught per hour
was allocated among the age classes by year by multiplying the percentage
frequency of each age c l a s s i n Table 3 by the number caught per hour.
The numbers of f i s h caught per hour by sex and age c l a s s a r e shown i n
Table 4.
These d a t a were then rearranged by year c l a s s f o r c e r t a i n age
groups as shown i n Table 5.
-
Year c l a s s strength
Year c l a s s strength was determined f o r year classes 1941-55 f o r age
groups 7-13. Year classes of 1941-43 were su2erior t o any of the
year classes following (Figure 5).
There i s a steady decline i n yeas
c l a s s strength from 1941-44 followed by a small surge i n 1945.
There
was f u r t h e r decline from 1945 u n t i l 1952 a t which time year c l a s s strength
has s t e a d i l y increased.
The 1955-56 year classes, though much stronger
than i n t h e e a r l y 1950qs, a r e s t i l l i n f e r i o r t o t h e 1941-43 year classes.
Year c l a s s strength of p e t r a l e s o l e o f f southern Vancouver Island,
British Columbia, as calculated by Ketchen and Forrester (1966), a r e
nearly i d e n t i c a l with respect t o the trends shown f o r Dover sole.
This
suggests t h a t oceanic conditions determine year c l a s s strength.
1/
Lengthweight fomuZae are W = 0.012668- 9153 mrd W = 0.001002 3.0302
for mates and fernate8 respsotivety, where W = grams atld L = cent<meters. Crams were converted t o pounds by dividing &er
of gram8
by 453.6.
Table 3.
Age composition (per cent frequency) of
Dover sole from PMFC area
3A
Age
Year
4
S
(4
2
E
9,
10
li
I2
-
Males
13
'
14
iS
'f6
17
18
3.9 20 >2'!
of
fish
Ave
age
.
Table 3. Continued
Age
Year
* 4
5
6
7
8
9
1n
11
12
Females
lJ
Age c q o 8 i t i m is the mepage of y e m 1948 and 1952,
O t o Z J t h s not mad beyond 13 yaws.
15
'4
15
re
,
1'7
..J&-!4
2
u
-
of
Ave.
fish
Table 4,
-
-
Year
5
Numbers of Dover sole caught by age group per hour
per significant landing from area 3A
--
Age
6
7
8
g
10, 11 12
-
Males
Females
13
-
14
15
16
17
18 19 20 >20
Table 5.
Age
Numbers of Dover s o l e , ages 7-13, caught p e r hour per s i g n i f i c a n t landing from a r e a 3A,
Data arranged by year c l a s s f o r year c l a s s e s 1941-55. Data taken from Table 4.
Year class
1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955
Males
-
Total
199
161
147
109
118
100
102
95
99
89
88
69
84
102
103
Females
Total
205
158
149
116
149
140
99
90
95
106
99
78
76
109
134
Combined
sexes
total
404
319
296
225
267
240
201
185
194
195
187
147
160
211
275
xnoq sad aq%m:,y s ? ~30 ssaqumN
LITERATURE CITED
Harry, G . Y. Jr.
1959,
Time of spawning, length at maturity and fecundity
Ketchen, K. S . and C. R. Forrester. 1966. Population dynamics of the
Petrale sole [Eopsetta jordanQ in waters off Western Canada. Fish
Res. Bd. Can. Bull. No. 153, 195 pp.