COMMERCIAL CLAM
CLAM PRODUCTION
PRODUCTION
COMPLETION REPORT
October 1,
to December 31,
31, 1981
1, 1979 to
by
Thomas
F. Gaumer
Thomas F.
Richard M.
M. Starr
Department of
of Fish
Fish and
and Wildlife
Wildlife
Oregon Department
Fisheries Service
Service
National Marine Fisheries
National Oceanic
Oceanic and
and Atiirspheric
Atmospheric Administration
Administration
United States
States Department of Commerce
Commercial Fisheries Research and
and Development
Development Act
Act
Commercial
Project
Project Number 1-lSO-R-2 Segment 22
Contract Number Sl-ABD-ORAB
8l-ABD-ORAB
March, 1982
1982
TABLE OF CONTENTS
Page
INTRODUCTION • . • . ...........................
. . . . • •
INTRODUCTION
11
ASSESSMENT OF HARVEST
POTENTIAL
ASSESSMENT
OF HARVEST
POTENTIAL ................. 11
Results
and and
Discussion
Results
Discussion ..................... 11
Yaquina Bay Bay ......................... 11
Yaguina
Coos Bay Bay
. . • ............................
. .
Coos
77
,
COMMERCIAL
CLAM CLAM
HARVESTHARVEST ......................
COMMERCIAL
8
Results
and and
Discussion
Results
Discussion
.....................
8
EFFECTSOFOFHARVEST
HARVEST
ON RECRUITMENT
AND HABITAT ...........11
11
EFFECTS
ON RECRUITMENT
AND HABITAT
Results
Discussion
......................11
Results and and
Discussion
.
11
MANAGEMENT
CONSIDERATIONS
.12
MANAGEMENT
CONSIDERATIONS .................... 12
LITERATURE
CITED CITED
. . . . .......................... 16
LITERATURE
.16
TABLES
Number
11
Page
Population and
and Biomass-Estimates
Biomass Estimates of.
of· Subtidal Clams
Clams
Population
in
Yaquina
Bay, 1975-81.
...
.
in Area
Area2, 2,
Yaquina
Bay, 1975-81
..............
44
22
of Subtidal
Subtidal Gaper
Gaper
Recruitment Estimates by Year-Class, of
Clams
ClamsininArea
Area
2, 2,
Yaquina
Yaquina
Bay, Bay,
1975-81.
1975-81
• . . ........... 44
33
Mean Age (yrs)
(yrs) of Clams
Clams Sampled from
from Area
Area 2,
2, Yaquina
Yaquina
Bay,
. .
• •. ,
Bay,1975-81.
1975-81
........................
•....
. . 55
44
Mean Length
Length (mm)
(mm) of Clams
Clams Sampled
Sampled from
from Area
Area 2,
2, Yaquina
Yaquina
Bay, 1975-81.
. . . ........................
. . . . . . . . .
. • 5S
Bay,
1975-81
55
Cohorts of
of Gaper
Gaper Clam,
Clam,
Estimated Abundance of Various Cohorts
Area 2,2,Yaquina
Bay,Bay,
Oregon,
1975-81.
. . • ............
. .
. . . 66
Area
Yaquina
Oregon,
1975-81
6
6
Estimates of Subtidal Clams
Population and Biomass Estimates
Clams in
Pigeon Point
Bay, 1975 and 1980
1980..........
. . . ..
. . 77
Point Area,
Area, Coos Bay,
7.
Summary of
of Numbers
Numbers of
of Penn-its
Permits Issued
Summary
rssued to
to Commercial
Commercial Clam
Harvesters,
1976-81.
.
8
Harvesters,
1976-81 ....................
8
8
8
Summary of Harvest (lbs)
(lbs) and
and Catch/Effort
Catch/Effort (lbs/hr)
(lbs/hr) for
for
Subtidal Clams,
Clams, 1975-81
1975-81. .
Commercially Harvested Subtidal
7.
99
10
. .
.......
99
Summary of
of Year-Class
Year-Class Composition
Composition (in
(in Percentage)
Percentage) of
of
Summary
Commercially Harvested Gaper Clams,
Clams, 1976-81
1976-81.
. .10
........
10
Lengths (mm)
(mm) of
of Commercially
Commercially Harvested
Harvested
Summary of Mean Lengths
Gaper
Clams,
1976-81 ....................
Gaper Clams,
1976- 81..
. . 10
10
11
11
Densities (No./ft2)
(No./ft 2) in
in Treatment
Treatment and
and
Summary of Clam Densities
Control Sites, Plot
Plot CC of
of Area
Area 2,
2, Yaquina
Yaquina Bay,
Bay, 1978-81.
1978-81 . . . 15
15
.
.
FIGURES
Number
1
1
2
2
Page
of Yaquina Bay,
Bay, Showing Areas Approved for
for
Map of
Commercial Clam Harvest . . . . . . . . • .
2
2
Map of Lower Coos Bay,
Bay, Showing Area
Area Approved
Approved for
for
Commercial Clam Harvest . . . . . . . . . • .
3
3
.................
.................
COMMERCIAL CLAM PRODUCTION
ABSTRACT
We completed
completed our
Our assessment
assessment of
of commercial
commercial clam
clam harvest
harvest potential
potential in
in
Tillamook, Yaquina
Yaquina and
and Coos
Coos bays.
bays. All three bays contained
contained commercial
commercial quantiquantities of
of clams.
clams. Detailed studies
studies in Yaquina Bay in 1981
1981 revealed
revealed aa biomass
biomass
ties
estimate of 2.6 million pounds (1,179.1
(1,179.1 mt)
mt) of
of gaper
gaper clams
clams (Tresus
(Tresus capax)
capax) in
in
tract.
the study tract.
Our studies showed
showed strong
strong recruitment
recruitment and
and survival
survival of
of gaper
gaper set
set in
in 1975.
1975.
Since then survival
survival of
of set
set has been negligible.
Estimates
Estimates of instantaneous
instantaneous rates
rates of natural
natural mortality
mortality for
for eight
eight gaper
gaper
clam cohorts
cohorts ranged
ranged from
from 0.12
0.12 to
to 0.89.
0.89.
The
commercial clam
clam harvest in
in Oregon
Oregon was
was entirely
entirely in
in Coos
Coos
The experimental commercial
Bay during 1980 and
and 1981.
1981. Poor market
market conditions
conditions eliminated
eliminated the
the fishery
fishery from
from
Yaquina Bay.
Bay.
Pwnp
Pump harvesters
harvesters reported aa catch
catch per
per hour
hour of
of effort
effort of
of 432
432 pounds/hr
pounds/hr
(196
kg/hr),
nearly
twice
the
harvest
rate
of
jet
harvesters.
(196 kg/hr), nearly
jet
The effects
recruitment and
and habitat were
were evaluated.
evaluated. Analyeffects of harvest on recruitment
sis of variance
variance revealed that
that densities
densities of only
only two
two species
species of
of clams
clams (li
(littlesis
ttleand macomas),
macomas), and amphipods
arnphipods and anemones
anemones were significantly different
necks and
different
in the treatment and control
control sites at
at the
the 95%
95% confidence
confidence level.
level.
Sediments in post-harvested areas showed
showed aa significantly
significantly higher
higher percentpercentage
at the
the 95%
95% confidence
confidence level.
leveL
age of coarse material at
INTRODUCTION
This
of the final
final two years of
of our
our conconThis report swnmarizes
summarizes the results of
on the
the bay clam
clam resources
resources in
in Oregon's
Oregon's major
major estuaries.
estuaries. A
A
tract studies on
completion report documenting the
the first
first three years of
of our
our work was submitsubmi t1976 (Gaumer,
(Gaumer, 1976).
1976). The
report described laboratory clam rearing
ted in 1976
The report
studies,
clam planting
planting work, and
and clam
clam surveys
surveys performed
performed from
from 1973
1973 to
to 1976.
1976.
studies, clam
The second
second phase of
of our
our studies
studies was summarized
summarized and
and further
further reported
reported distridistribution and commercial
commercial potential of
of Oregon
Oregon bay
bay clams
clams (Hancock,
(Hancock, et
et al.
a1. 1979).
1979).
reports have
Three annual progress
progress reports
have been
been prepared
prepared since
since 1979
1979 which
which reported
reported
of harvest potential and
and effects
effects of
of harvest
harvest upon
upon recruitment
recruitment
assessment of
(Gaumer,
1982).
(Gaumer, et
et al.
al. 1979;
1979; Gaumer and Robart,
Robart, 1980;
1980; Gaumer and Starr,
Starr, 1982).
The
of all report
report periods have been: (1)
The objectives of
(1) to
to refine techfor assessing
assessing the potential for a commercial
commercial clam fishery
niques for
fishery in
in several
several
of Oregon's estuaries and in offshore
offshore locations
locations along the
of
the southern
southern Oregon
Oregon
coast and (2)
(2) to develop aa scientifically sound
sound clam
clam management
management data
data base.
base.
HARVEST POTENTIAL
POTENTIAL
ASSESSMENT OF HARVEST
As a result
result of our
Our clam
clam distribution studies
As
studies conducted between
between 1973
and 1979,
thin Tillamook,
1979, several
several areas
areas wi
within
Tillamook, Yaquina
Yaquina and
and Coos
Coos bays
bays were
were found
found to
to
contain
commercial quantities
contain what
what appeared to
to be
be commercial
quantities of
of subtidal
subtidal clams
clams (Gaumer
(Gaumer
and Lukas,
Lukas, 1975; Gaumer and
and Robart,
Robart, 1980).
1980). Studies
Studies conducted in
(Gaumer
in 1976
1976 (Gaumer
and Halstead,
1976) revealed
revealed that commercial
commercial quantities
quantities of
of subtidal
subtidal clams
clams
Haistead, 1976)
certain portions of
of these
these three
three bays.
bays.
existed in certain
originally planned
planned to
to inventory
inventory subtidal
subtidal clams
clams off
off the
the
Although we originally
Oregon coast,
coast, the
the studies
studies did
did not
not materialize
materialize during
during the
the contract
contract
southern Oregon
period. The commercial fishermen
fishermen that
that expressed an interest in aa joint
joint exexwere unable
unable to
to obtain
obtain the
the state
state and
ploratory survey with our Department were
federal
fill and removal
removal permits necessary
necessary to
to conduct
conduct the
the surveys.
surveys.
federal fill
This
results of
of our
our studies
studies in
in Yaquina
Yaquina and
and Coos
Coos
This section summarizes the results
bays.
(7.4 ha)
(Figure 1),
The Yaquina test plot encompassed 18.4 acres
acres (7.4
ha) (Figure
1), whereas
whereas
the
Coos Bay site covered
covered 48.0 acres
acres (19.4
(19.4 ha)
ha) (Figure
(Figure 2).
2).
the Coos
Results and Discussion
Discussion
Results
Yaquina Bay
Yaguina
shows the population and biomass
Table 1 shows
biomass estimates
estimates of clams
clams collected
from Area 22 of
of Yaquina Bay
Bay since
since 1975.
1975. Gaper clams (Tresus capwr)
capax) and macoma
clams (Macorria
(Macoma inquinata)
the two principal
principal species
species encountered.
encountered. Other
inquinata) were the
species
the cockle (Clinocardium
species included the
(Clinocardiwnnuttallii),
nuttallii), native littleneck
eVenerupis
staminea),
butter
(SaxidiJrrrus
giganteus)
(Tfenerupis stominea),
(SaxidDinus giganteus) and piddock (Zirfaea
CZirf'aeapilsbryi)
pilsbryi)
clams.
clams •
Gaper clams,
clams, the target species
species for
for the
commercial fishery,
the commercial
fishery, had
had an
estimated peak population of 36.3 million clams
clams in
in 1975
1975 and decreased in
in numbers
numbers
to a population low
low of
of 6.2
6.2 million
million clams
clams in
in 1981.
1981. A
A corresponding decrease in
US HWY tot flOUt
gMlO,t
C#4M4tg.
C~I/NIWL
~.
I
t%)
N
I
BOAT BASIN
BASIN
SOAT
oOSU
SU
SOUTH
SOUTH 8CACP4
SEACH
PLAN
IClO
lOG ItXI • ,
, . lllIOt.
'?°?
!°°'!°
''I,
'II'
Q
Figure 1.
1.
Map of
of Yaquina
Yaquina Bay,
Bay, Showing
Showing Areas
Areas Approved
Approved for
for Commercial
Commercial Clam
Clam Harvest.
Harvest.
MARINE SCIENCE
SCIENCE
MARINE
CENTER
-3-3-
I.
~-IY:"'--:PeRM
AR<;;A
Goos"BtAy
Uo0
Figure
2.
Figure 2.
tO
1000
q
woomr
Clam Harvest.
Map
of Lower
Lower Coos
Coos Bay,
Bay. Showing
Showing Area
Area Approved
Approved for
for Commercial
Commercial Clam
Harvest.
Map of
-4-
estimated biomass was also
also recorded.
recorded. Gaper clan
clam biomass decreased from
from over
over
5.1 million
million pounds
pounds (2,267.6
(2,267.6 mt)
mt) in
in 1975
1975 to
to 2.6
2.6 million
million pounds
pounds (1,179.1
(1,1791 mt)
5.1
mt)
in 1981.
1981.
in
The principal
principal reason
reason for
for this
this decline
decline was
was the
the nearly
nearly complete
complete lack
lack of
of
annual
(Table 2).
2). No recruitannual recruitment since
since a very
very successful set in 1975 (Table
ment has been realized from
from the 1978 to 1981 year-classes.
year-classes. Spawning and
and juvejuvenile settlement occurred each year,
year, but survival
survival was negligible. Mean gaper
clam densities ranged
ranged from
from aa high
high of
of 45.4/ft2
45.4/ft 2 (488.7/rn2)
(488.7/m2 ) in
in 1975
1975 to
to aa low of
2
2
7.7/ft (82.9/rn2)
(82.9/m ) in 1981.
1981. Several of the individual samples collected
collected in
in 1975
1975
7.7/ft2
2 (2,153.0/m2).
contained gaper set
(2,153.0/m2).
set in excess
excess of 200.0/ft
200.0/ft2
Table 1.
1.
Population and Biomass
Clams in
in Area
Area 2,
2',
Biomass Estimates of Subtidal Clams
Yaquina
Bay, 19
1975-81.
Yaquina Bay,
75-81.
Numbers
Species
cies
1975
1976
1977
Gaper
Cockle
Cockle
Littleneck
Butter
Macoma
Piddock
36,300,000
183,200
366,400
416,000
13,532,800
1,700,000
25,566,400
16,800
216,800
333,600
20,566,400
29,316,000
Total
52,498,400
46,700,000
1975
1976
5,084,200
5,217,200
Species
Gaper
Table 2.
2.
YearClass
1975
1976
1977
1978
1979
1980
1981
o
1978
o
0
116,000
200,000
12,049,600
o0
0
41,681,600
10,560,000
32,000
48,000
240,000
11,200,000
o0
22,080,000
Biomasss (lbs)
(ibs)
Biomas
1977
1978
4,968,991
4,136,800
1979
1980
11,116,700
16,700
133,300
200,000
10,100,000
11,050,000
0
0
o
21,566,700
1979
3,461,100
1981
6,160,000
0
o0
66,700
366,700
10,100,000
120,000
200,000
5,968,000
o
o
o0
12,448,000
21,583,400 12,448,000
1980
1981
4,265,600
2,569,700
Recruitment Estimates
Year-Class, of
of Subtidal
Subtidal Gaper Clams
Clams in
Estimates by Year-Class,
in Area
Area 2,
2, Yaquina
Bay,
Bay, 1975-81.
1975
1976
28,894,800
18,995,800
25,500
25,500
Numbers
1977
1978
24,742,700
351,800
29,300
5,786,900
570,200
211,200
00
1980
1979
9,666,700
150,000
16,700
1981
-
-
-
-
-
-
-
-
-
-
-
-
-
-
9,414,600
165,800
0
0
0
0
00
00
-
-
-
-
-
-
-
0
0
00
5,427,000
18,500
18,500
0
0
0
0
0
0
0
0
-5-5--
Mean age composition
compOSl. tl.on of
of clams
clams sampled
sampled from
from Area
Area 22 is
is shown
shown in
in Table
Table 3.
3.
The steady increase in age,
age, since
since 1975,
1975, for
for gaper,
gaper, butter
butter and
and littleneck
littleneck clams
clams
reflects
of strong
strong recruitment
recruitment from
from the
the 1974
1974 and
and 1975
1975 year-classes
year-classes
reflects the
the impact of
1975 to
to 1981 gaper clams increased in
and weak
then. From 1975
weak recruitment since then.
mean
years, butter
butter clams
clams increased
increased from
from 3.2
3.2 years
years
mean age
age from 0.6
0.6 years to 6.3 years,
to 10.5
10.5 years
clams increased
increased from
from 1.5
1.5 years
years to
to 6.1
6.1 years.
years. Too
years and littleneck clams
few
few cockle
cockleclams
clams were
were collected
collected to
to show
show aa trend.
trend.
Table 3.
3.
2, Yaquina Bay,
Bay, 1975-81.
Mean Age
Age (yrs)
(yrs) of
of Clams
Clams Sampled from Area 2,
Species
Gaper
Cockle
Butter
Littleneck
1975
1976
1976
0.6
0.9
3.2
3.1
3.1
4.5
45
-
-
7.9
5.1
7.8
3.9
1.5
1977
1977-
Year
1978
1978
1979
1980
1981
4.1
3.0
7.9
7.9
5.3
4.4
5.3
6.3
-
-
11.3
11,3
5.3
9.1
4.8
-
10.5
6.1
Table 44 displays the mean length composition for the same
four species
same four
species of
clams.
Mean lengths
lengths of gaper clams increased from 36.9
to 91.7
91. 7 rom
36.9 rom
mm in 1975 to
mm
in 1981. Butter and littleneck clams
clams exhibited similar increases in
in mean
mean sizes.
sizes.
Table 4.
4.
(mm) of
of Clams Sampled from Area
Yaquina Bay,
Length (rom)
Area 2,
2, Yaquina
Bay, 1975-81.
Mean Length
Year
Species
Gaper
Cockle
Butter
Littleneck
1975
1976
1977
1978
1979
1980
1981
36.9
20.5
35.4
24.4
76.0
13.0
63.4
45.3
65.9
90.8
47.5
75.3
57.3
83.2
88.7
91.7
91.
7
-
86.1
46.3
-
83.2
56.3
-
76.0
44,0
44.0
-
75.3
50.0
50,0
estimated abundance
abundance with time
time to obtain estimates
We regressed estimated
estimates of natural
mortality for eight gaper
gaper clam
clam cohorts.
cohorts. Estimated instantaneous rates
rates of
natural
(M) ranged
ranged from
from 0.12
0.12 to
to 0.89
0.89 (Table
(Table 5).
5). This wide range
range may
may
natural mortality (M)
be
due to
fact that the
the estimates
be partially
partially due
to the
the fact
estimates of M
M are
are only as
as reliable
reliable as
as
The most
most reliable
reliable abundance estimates are those
of abundance.
abundance. The
the estimates of
which came
came from large
(because
large samples
samples and are
are for clams
clams younger than
than 55 years
years (because
Therefore, the 1972, 1975,
difficulty in aging
aging clams
clams older
older than
than 55 years).
years). Therefore,
of the difficulty
and 1976
1976 year-class
year-class abundance
abundance estimates
estimates are
are the
the most
most reliable
reliable for
for the
the 1975
1975 to
to
1981
Estimated MM for
for those year-classes exhibited a
a narrower range
1981 time period. Estimated
from 0.33 to 0.50.
5.
Table 5.
Estimated Abundance of
of Various Cohorts
Cohorts of
of Gaper
Gaper Clam,
Clam, Area
Area 2,
2, Yaquina
Yaquina Bay,
Bay, Oregon,
Oregon, 1975-81
1975-81
YEAR
May
1977
Feb~
Feb;
March
1978
1979
March
1980
1980
Year
Class
Sept.
1975
Oct.
1976
1967
395,800
151,200
89,379
45,815
17,502
-
1968
1,193,200
295,750
138,040
53,080
-
1969
1,627,700
617,150
366,610
1970
981,720
470,080
1971
250,600
218,960
March
1981
M
M
-
-
0.89
12,988
-
-
0.12
185,280
70,249
--
-
-
0.89
314,380
188,520
90,272
45,649
23,084
0.68
203,400
185,210
161,830
142,820
126,050
0.12
I
'"
C.'
I
1972
2,031,300
1,180,900
878,090
602,500
350,270
211,980
128,290
0.50
1975
42,663,000
29,851,000
24,560,000
19,166,000
13,410,000
9,634,700
6,922,000
0.33
1976
--
611,020
494,110
364,620
245,530
170,250
118,050
0.36
-7-
Bay
Coos Bay
Analysis
48-acre (19.4
(19.4 ha)
Analysis of our data showed the 48-acre
ha) clam bed
bed in
in Coos
Coos Bay
Bay
contained an estimated 3.7
3.7 million clams
clams in 1980
1980 (Table
(Table 6).
6). This
This represented
a net loss of
of approximately
approximately 22.7
22.7 million
million clams
clams since
since our
our 1975
1975 survey.
survey. The
a
only species not realizing
realizing aa dramatic
dramatic decrease
decrease in
in numbers
numbers was
was the
the piddock
piddock clam.
clam.
The dredging
dredging of
of the
the nearby
nearby main
main ship
ship channel
channel during the 1975-80 time period
contributed to
to the
the reduction
reduction of
of clams
clams in
in the
the harvest
harvest bed.
bed. Post dredge
may have contributed
observations revealed
revealed what appeared
appeared to
to be
be more
more fluid
fluid sand
sand over
over much
much of
of the
the area.
area.
Whatever the
the reason
reason for
for the
the population decline,
decline, we believe that the
the commercial
commercial
Whatever
area had
had little
little impact
impact on
on the
the availability
availability of
of harvestable
harvestable clams.
clams.
fishery in the area
300,000 clams,
clams, mainly
mainly gapers,
gapers, were
were removed
removed from
from the
the area
area from
from 1975
1975
Less than 300,000
small portion
portion of
of the
the plot
plot was
was worked.
worked.
to 1980, and only aa small
As
gaper and
and macoma
macoma clams
clams were
were the
the principal
principal species
species recorded.
recorded.
As in 1975, gaper
Mean gaper clam densities
densities ranged from a high of 2.7fft2.
(29.lfm2.) in
2.7/ft2 (29.1/m2)
in 1975
1975 to
to
0.3fft2.
(3.2fm2.) in
0.3/ft2 (3.2/m2)
in 1980.
1980. Biomass
Biomass estimates
estimates during that
that same
same time
time period
period
decreased from
from 484
484 mt
mt to
to 210
210 mt.
mt.
Table 6.
6.
Estimates of Subtidal
Subtidal Clams
Clams in
in Pigeon
Pigeon Point
Point
Population and Biomass
Biomass Estimates
Area,
Bay, 1975 and
and 1980.
1980.
Area, Coos Bay,
1975
Species
Gaper
Cockle
Li ttleneck
Littleneck
Butter
I
rus
Irus
P1 ddock
Piddock
Petri
cola
Pet rico
1 a
Bentnose
Cryptomya
Bodega
Bode
ga
5,648,700
202,200
843,000
809,200
16,018,600
16,018,600
0
0
101,000
2,647,300
67,300
101,000
Total
26,438,300
1980
Biomass (lbs)
Biomass(lbs)
Number
Number
1,530,800
606,400
23,000
16,900
71,600
151,800
248,200
236,100
.236,100
Not Calculated 2,428,100
252,900
"
"
00
"
"
00
"
"
00
"
"
00
"
"
.
II
II
It
1,873,600
3,692,200
(lbs)
Biomass (lbs)
464,400
Not Calculated
"
"
"
"
I'
11
"
"
"
"
"
"
"
It
"
"
II
"
"
"
II
It
464,400
Gaper clams
clams in the
the Coos
Coos Bay survey area had aa mean age
age of 2.6
2.6 years
years in
in
1976 and 5.7
5.7 years
years in
in 1980.
1980. Similar to Yaquina Bay,
Bay, recruitment
recruitment was
was sporadic
near total
total failure
failure of
of the
the 1975-1979
1975-1979 year-classes.
year-classes. The loss of
of the 1975
1975
with aa near
year-class
since this
year-class is
is particularly disturbing since
this year-class
year-class is
is dominant in
in
Netarts, and
and Tillainook
Tillamook bays.
Yaquina, Netarts,
Mean length of
of gapers
gapers was
was 65.7
65.7 mm
mm in
in 1975
1975 and
and 102,8
102.8nun
mm in 1980.
1980.
-8-
COMMERCIAL CLAM
CLAM HARVEST
HARVEST
COMMERCIAL
As aa result
result of our clam assessment surveys,
surveys, selected areas
areas within
within
fishYaquina and Coos
Coos bays were
were approved for an experimental commercial
commercial clam fishery (Figures
ery
(Figures 1 and 2).
2). The fishery
fishery was
was designed to
to study
study the
the effects
effects of
of
mechanical clam harvesting equipment on the
resources and benthic enmechanical
the clam resources
Two types of
of harvest equipment
equipment were
were permitted:
permitted: a high pressure
pressure
vironment.
hand-held water jet
jet and
and aa suction
suction pump.
pump. Specific areas were designated within
in Coos
Coos Bay
Bay was
was
in Yaquina
Yaquina Bay for jet or pump harvest.
harvest. The entire unit in
jet or pump.
pump. A
A qoota
qwta of
of 10%
10% of
of the
the available
available gaper
gaper clam
clam bioopen to either jet
selected for
for harvest
harvest from
from each
each permit
permit area.
area. The season
mass was arbitrarily selected
and ended
ended Decether
Decenber 31
31 for
for each
each year.
year. Monthly accounts reportreportstarted July 1 and
ing
ing pounds
pounds and
and numbers
numbers of
of clams
clams harvested
harvested and
and hours
hours of
of effort
effort were
were required
of each harvester.
Table
Table 7 is
is aa stn1Dl1ary
summary of the nunber
nunber of clam diggers
diggers we
we issued permits to
renove clams
clams from Yaquina and Coos
Coos bays
bays from 1976-1981.
mechanically remove
1976-1981. To date,
most interest
interest has
towards the use of a high pressure water jet in Coos
nnst
has been towards
Bay.
Bay.
Table 7.
7.
Stn1DI1ary
Harvesters,
Summary of Numbers of Permits Issued to Commercial Clam Harvesters,
1976-81.
Yaquina Bay
Pump
Jet
Jet
1976
1977
1978
1979
1980
1981
Total
11
2
2
2
2
°1
0
1
2
8
8
11
33
22
22
11
11
10
...
Coos
Coos Bay
Pump
11
1
1
3
3
°°11
4
4
4
11
11
15
15
4
4
2
2
_-
0
0
1
1
Results
Results and Discussion
The
fisheries in Yaquina and Coos bays produced
produced
The experimental
experimental clam fisheries
291,088 pounds
pounds (132
(132 mt) and
and 290,867
290,867 pounds
pounds (132
(132 nit),
mt), respectively
respectively (Table
(Table 8).
8).
The
(90.3 mt)
mt) were landed
landed and
and
The harvest
harvest peaked in 1978 when 199,162 pounds (90.3
steadily declined to
pounds (28.1
(28.1 mt)
mt) in
in 1981.
1981. In
to aa low of 61,955 pounds
In 1980
1980 and
1981,
1981, only Coos
Coos Bay
Bay fishermen
fishermen produced
produced clams.
clams. Poor market conditions
conditions and
the
the availability
availability of cheap east coast clams contributed
contributed to this lower
lower harvest.
Although
to both jet
jet and
and pump
pump harvesters
Although harvest permits were issued to
of harvesters reported no take.
take. Several
Several
for most
most years
years in each bay,
bay, a number of
of these fishermen
fishermen confided
confided in
in us
US that
that they
they reapply
reapply every
every year
year with
with no
no intenintenof
tion of fishing,
to be ready if a market develops.
develops.
fishing, but
but want to
-9-
effort was
Catch per hour of effort
was highest
highest for pwnp
pump operators
operators in
in Yaquina Bay
where they took
432
pounds/hr
(196
kg/hr).
took
potmds/hr (196 kg/hr). Surprisingly,
in
Surprisingly, jet operators in
Yaquina and Coos
Coos bays
clams at
at nearly the
bays harvested clams
the same
same rate;
rate; 243 pOtmds/hr
pounds/hr
(110
(109 kg/hr),
respectively.
(110 kg/hr)
kg/hr) vs.
vs. 239
239 potmds/hr
pounds/hr (109
kg/hr), respectively.
Table 8.
8.
Summary of
of Harvest (lbs)
(ibs) and Catch/Effort
Catch/Effort (lbs/hr)
(lbs/hr) for Commercially
Harvested Subtidal Clams,
Clams , 1975-81.
Jet
1976
1977
1978
1979
1980
1981
0
0
38,505
9,103
00
00
00
Total
47,608
Yaquina Bay
Pwnp
C/Hr
Pump
00
C/Hr
Jet
Coos Bay
Pump
Pwnp
C/Hr
C/H
C/Hr
00
00
00
0
0
15,600
153,315
74,565
0
0
0
0
00
129
486
593
0
00
103,584
11,931
36,744
13,901
62,752
61,955
226
157
250
287
282
235
0
00
0
0
00
00
00
00
0
0
0
243
243,480
432
290,867
239
0
0
00
307
128
00
0
0
0
0
Table 9 exhibits the year-class composition
compos~t~on of commercially
commercially harvested subtidal
clams taken
taken from
from Yaquina
Yaquina and
and Coos
Coos bays
bays from
from 1976-1981.
1976-1981. Yaquina
tidal gaper clams
Bay data revealed that
the 1970-1972
that the
1970-1972 year-classes
year-classes were
were the
the principal
principal age
age groups
groups
taken
taken in 1977
1977 and
and 1978.
1978. In
In 1979
1979 the
the 1975 year-class
year-class became
became important in
in the
the
take,
of the harvest. No harvest was reported
reported for 1980 and
take, producing over 67% of
1981. Mean ages
ages of harvested
7.4 and
and 4.8
4.8 years
years in
in 1977,
1977,1978
harvested clams
clams were
were 5.7,
5.7,7.4
1978
and 1979, respectively.
respectively.
It
It was
was difficult
difficult to
to determine
determine if pwnp
pump and jet
jet operators
operators were
were selectively
selectively
harvesting
gaper clams
clams by
by size.
size. Table 10 shows that
that in
in 1977
1977 gaper
gaper clams
clams taken
taken
harvesting gaper
by jet operators
operators in Yaquina Bay averaged 116.0 mm in length,
length, whereas
whereas pump
pump
In 1978,
1978, the
the mean
mean length of pump harvested
harvested gapers
gapers averaged
averaged 109.1
109.1 mm.
rom. In
clams was 26.6
26.6 mm
rom larger
larger than
than those
those taken
taken by
by jet.
jet.
clams
Data collected
collected from Coos
Coos Bay harvested gaper clams
clams showed aa wide
wide range
range of
year-classes represented
represented in
in the
the take.
take. In
In contrast to
to Yaquina Bay,
Bay, the 1975
The mean
mean age
age of
has never
never been
been aa large
large contributor
contributor to
to the
the harvest.
harvest. The
year-class has
clams ranged from
from 6.2 years in
in 1978
1978 to
to 8.9
8.9 years
years in
in 1980.
1980. Jet harvested
harvested gapers
gapers
clams
larger in
in Coos
Coos Bay
Bay than
than in
in Yaquina
Yaquina Bay
Bay (Table
(Table 10).
10).
were generally larger
-10-
Summary of
of Year-Class
Year-Class Composition
Composition (in Percentage)
Percentage) of Commercially
Summary
Harvested
Harvested Gaper
Gaper Clams,
Clams, 1976-81.
1976-81.
Table 9.
9.
YearClass
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1976
----------------
1977
---
Yaquina Bay
1978 1979 1980
1980
--
<0.1
0.7
1.8
8.5
17.2
29.8
25.4
6.7
2.0
7.8
0.1
0,2
0.2
1.0
5.9
5,9
12.3
25.8
31.0
16.7
5.2
0.7
1.1
----
----
5.7
7.4
1981
1976
1977
Coos Bay
1978 1979
1,
!J
--
1,
Y
--
-----------
107
1.7
5.9
50.0
3.4
0.0
0.4
3.4
5.0
27.7
2.1
0.4
----
---
---
--
0.9
7,2
7.2
27.0
28.8
28,8
18.0
15.3
0.9
108
1.8
--
---
4.9
14.0
20.7
15.8
43.5
1.1
---
---------------
-----
-----
-----
-----
4.8
--
--
7.8
6.9
6,2
6.2
----
0.4
0.4
0.0
0,0
1.6
4.3
7.8
8.3
8.8
67.2
1.2
--
1980
1981
--
----
--
0.6
9.0
5.8
26.9
26,9
37.5
9.0
8.7
2.6
0.3
0.3
4.7
9.4
14.5
25.6
33.7
10.4
0.7
0,3
0.3
2.1
12.8
42.6
29.8
12.8
----
----
----
7.3
8.9
7.6
--
----
Mean
Me
an
Age
(Yrs)
(Yrs)
1/
!J
--
No
during these
these years.
years.
No commercial harvest during
10.
Table 10.
Year
1976
1977
1978
1979
1980
1981
Summary
(mm) of Commercially Harvested
Harvested Gaper
Gaper Clams,
Clams,
Summary of
of Mean
Mean Lengths
Lengths (mm)
1976-81.
19 76-81.
Bay
Yaquina
Yaguina Bay
Jet
Pump
--
109.1
123.5
101.6
---
--
116.0
96,9
96.9
----
Coos Bay
Coos
Pump
---
-----
Jet
133.1
132.6
121,2
12102
126.4
133.7
133.7
132.3
-11-11-S
EFFECTS OF HARVEST ON RECRUITMENT AND HABITAT
concerns with aa new
One of our primary concerns
new commercial
commercial clam fishery
fishery was
was the
the
effect the harvest might
might have
have on
on recruitment.
recruitment. This is
is especially important
important
in Oregon since our estuaries are small in size and
and few
few in
in number. Ideally,
aa commercial
commercial fishery can harvest a portion of
of the
the existing
existing clams
clams without
without
affecting recruitment from
from surrounding
surrounding brood
brood stock.
stock.
location of
of our research
research facilities
facilities most
most of
of our
our field
field activiacti viDue to the location
ties
Yaquina Bay.
Bay. This
This segment
segment reports
reports the
the results
results of
of our
our
ties were
were limited to Yaquina
findings
Yaquina Bay.
Bay.
findings from Yaquina
Res ul is and Discussion
Dis cuss ion
Results
Although we originally planned to
to evaluate
evaluate the relative
relative effects
effects of
of aa water
water
jet
and surrounding
surromding habitat, little
little
jet vs.
vs. aa suction pump on clam recruitment and
measurable
precluded aa comparison.
comparison. As aa result,
result, we
measurable effort by jet harvesters precluded
were only able to measure the impacts
impacts caused by
by aa suction
suctiOn pump
pump in
in Plot
Plot C of
of
Area 2 in Yaquina
Bay (Figure
(Figure 1).
1).
Yaquina Bay
C was originally surveyed
surveyed in
in 1978
1978 and
and contained
contained 1.3
1.3 million
million clams,
clams,
Plot C
gapers weighing
weighing 358,900
358,900 pounds
pomds (162.7
(162.7 mt).
mt). Gapers
of which 0.4 million were gapers
inthe plot
plot averaged
averaged 118.8
118.8 mm
mm in
in length
length and
and397.2
397.2gins
gms in
in weight.
weight. Preharvest
sampling revealed a clam density
density of 21.6/ft2
21.6/ft 2 (232.5/m2).
(232.5/m2 ). Mean age
age was
was 6.4
years. A
A harvest quota of
of 200,000
200,000 pounds
pomds (90.7
(90.7 mt)
mt) was
was approved
approved for
for the
the site.
site.
A
established near
near the
the treatment
treatment area.
area. Gaper clams
A control test plot was established
in
length and
and 411.8
411.8 gms
gms in
in weight.
weight. Mean
in the
the control plot averaged 120.3 mm in length
age was 6.4 years.
years. Our sampling revealed a clam
clam density
density of
of 64.4
64.4 clams/ft2
clams/ft 2
age
2 ) for
(695.5/m
area.
(695.5/in2)
for the
the control area.
working side
side by
by side
side removed
removed 153,315
153,315 pounds
pomds
Two suction pump operators, working
(69.5 mt)
gapers from Plot C
C in the fall
fall of
of 1978.
1978. The
(69.5
mt) or
or 43%
43% of the
the gapers
The harvested
harvested
clams
clams averaged 123.5 mm in length and 420.2 gms
gms in
in weight.
weight. Mean age
age was
7.4
was 7.4
years. Post harvest sampling in the fished area showed aa clam density
density of
of
2 (14.0/m2),
1.3/ft
(14.0/m 2), indicating aa nearly complete
complete removal
removal of
of clams,
clams. Approxi1.3/ft2
mately
mately 60%
60% of the test plot was harvested.
harvested.
Post harvest samples
samples were
were taken
taken twice
twice aa year,
year, spring and fall,
fall, from
from 1978
1978
to 1981 (Table
(Table 11).
11). Results
of
this
sampling
revealed
a
disturbing
fact
that
Results
this
a disturbing fact that
we have had poor survival of set
set of gaper and
and cockle
cockle clams
clams in Yaquina Bay in
in
both the treatment and
and control
control sites.
sites. Some
Some recruitment was
was evident
evident for butter
butter
and littleneck clams in both the harvest and
and control
control plots.
plots. Although we made
to age the macoma clams,
clams, populations
remain constant
no effort to
populations appeared to remain
constant for
for
this
throughout the
the test
test period.
period.
this species throughout
samples we found
found that 64 different species of marine
In the post harvest samples
organisms
organisms reestablished themselves
themselves in
in Plot
Plot C,
C, whereas
whereas 46
46 species
species were
were observed
observed
in the
(Gaumer et
et al,
aI, 1979).
1979). Mollusca,
and arthropoda
arthropoda were
the control (Gaumer
Mollusca, annelida and
in
all well
represented in
in the
the samples.
samples.
all
well represented
A two-way analysis of variance was
for possible
A
was applied to test for
possible variation
variation
due
due to
to temporal separation of sampling periods. Since
showed no
Since our data showed
-12-12-
variation due
due to
of
to sampling in different time periods,
periods, a one-way analysis of
as a more powerful test for
for evaluating
evaluating differences
differences in
in
variance was utilized as
number
of taxonoimic
taxonomic groups
and control.
control.
number of
groups between
between treatment and
Analysis of variance for
for our
our 1981 data
data showed that
that densities
densities of
of two
two
Analysis
clams (littlenecks
(littlenecks and macomas),
and anemones were
were
species of clams
macomas), and amphipods and
consignificantly different
different in
in the
the treatment
treatment and
and control
control sites
sites at
at the
the 95"'"0
9% confidence level.
level. Our 1980 data
data revealed
revealed no significant
significant differences
differences for
for the
the
fi
ve species of clams and
and 17
17 other
other taxa
taxa of
of benthic
benthic invertebrates.
invertebrates.
five
The
assessed
The impact
impact of the commercial clam harvest on habitat was initially assessed
observations. Post-harvest surveys
by visual observations.
surveys revealed little physical evidence
of the harvest,
harvest. Strong
strong tidal currents
currents in
in the
the area
area removed
removed nearly
nearly all
all evidence
evidence
of the
the fishery.
fishery.
of
Sediment analysis
analysis of the pre- and
and post-harvest samples
samples showed
showed the
the percentpercentages
COarse materials
ages of coarse
materials were generally higher in the post-harvest samples.
of gravel,
gravel, shell
shell and
and coarse
coarse sand
sand significantly
significantlY higher
higher at
at
We found percentages of
the 95% confidence
confidence level following
following harvest, whereas the
the percentage
percentage of
of fine
fine
the
sands was significantly
significantly lower.
lower. These
These data suggest
suggest that
that aa portion of the fine
sand was carried
carried away from
from the
the area
area during
during harvest,
harvest.
MANAGEMENT CONS
CONSIDERATIONS
MANAGEMENT
IDE RATIONS
The
to develop a scientifically sound
sound
The primary purpose
purpose of this
this study was
was to
data base.
base. The
analysis, accomaccomclam management data
The years
years of data collection and analysis,
funding, provided
provided our
our Department
Department with
with considerable
considerable
plished with PL 88-309 funding,
and basic
basic biology
biology of
of several
several species
species of
of bay
bay clams.
clams.
insight into the status and
Our commercial
commercial bay
bay clam management
management program
program was
was aided
aided by
by our
our research
research which
which had
had
follOWing findings
findings and
and considerations:
considerations:
the following
1.
1.
A
resource inventory of both
A resource
both the
the intertidal
intertidal and
and subtidal
subtidal clam
clam
stocks
completed and
and proprostocks in 11 of Oregon's major estuaries was completed
of information on species composition,
composition, distribudistribuvided aa wealth of
tion, relative densities,
densities, and
and habitat requirements.
requirements. Data were
tion,
also
sand shrimp
shrimp and
and vegetation,
vegetation. Our distribualso collected on sand
tional surveys
extensive; we examined over
over 518,000
518,000 meters
meters
tional
surveys were extensive;
of transect
transect which included over 9,200 stations.
2.
2.
of data
data were collected,
collected, analyzed
analyzed and
and
Although a large volume of
reported,
life
reported, considerable knowledge
knowledge of basic Oregon clam life
history is still needed.
3.
3.
provided new information
information on
on the
the location
location
The subtidal surveys provided
commercial harvest potential in
in Tillamook,
Tillamook,
of clam beds
beds having commercial
and Coos
Coos bays.
bays. Biomass
Biomass estimates
Yaquina and
estimates in these bays revealed
aa total
pounds (8,345
(8,345 mt)
mt) of
of clams.
clams. Yaquina
total of 18.4 million pounds
(4,717 mt), or
or 57%,
57%, of
of this
this
Bay contributed 10.4 million pounds (4,717
total.
For the three bays combined,
combined, gaper clams
clams comprised
comprised 74.5%
74.5%
of the
the total biomass.
-13-13--
4.
Gaper clams
beds in
inmany
many
Gaper
clamswere
werefound
foundassociated
associated with
with eelgrass beds
instances.
dense conconinstances. Few
Fewclams
clamswere
wereobserved
observedinin areas
areas having dense
centrations of
ofsand
sandand
andmud
mud shrimp.
shrimp. These
tend to
centrations
Theseresults
results tend
indicate
indicate the
the importance
importanceofofsubstrate
substratestability
stability to
to the
the settling
settling
and/or survival of
ofbay
bay clams.
clams.
and/or
5.
In 1975
an experimental
experimental commercial
commercialgaper
gaperclam
clamfishery
fisherywas
wasinitiiniti1975 an
ated in
inYaquina
Yaquina Bay.
Bay. Our
Our primary
primaryobjective
objective was
wastoto evaluate
evaluate the
the
impact
on clam
clam recruitment
Two types
impact of
of harvest
harvest on
recruitment and
and habitat.
habitat. Two
types
of
harvesting gear
gear were
and
of harvesting
were permitted--a
permitted--a high
high pressure
pressure water
water jet
jet and
a suction
suctionpump.
pump. Due
Due totothe
by jet
jet harvesters,
harvesters,
the lack
lack of
of effort
effort by
only
the
impact
caused
by
the
suction
pump
was
evaluated.
Little
only
impact caused by the suction pump was
Little
long
term
impact
by
the
suction
pump
on
recruitment
or
habitat
long term impact by the
pump on recruitment or habitat
was
area.
was noted
noted for
for the
the treatment area.
6.
Recruitmentof
of subtidal
subtidal clams
Recruitment
clams in
inYaquina
Yaquina Bay
Bay was
was found
found to be
be
annual
annual but
but survival
survival was
was sporadic;
sporadic; 1975
1975was
wasthe
thelast
last year
year for
for
high survival
survival of
of gaper
gaper clams.
clams. This
from fully underunderhigh
This precluded
precluded us
us from
standing the
the impact
of the
the fishery
standing
impact of
fishery on
on recruitment.
recruitment. This
This also
suggests
consideration must
must be
given to
allowsuggests that
that careful consideration
be given
to the allowable
acreage for
able acreage
for subtidal
subtidal harvest.
7.
Speciesdiversity
diversity in
in the treatment
plot returned
Species
treatment plot
returned to preharvest
preharvest
levels
within months
months of
levels within
of harvest.
8.
Suction
pumpharvesting
harvestingwas
wasconsiderably
considerablymore
moreefficient
efficient than water
Suction pump
water
jet
harvesting. Pump
jet harvesting.
Pumpoperators
operatorswere
wereable
abletotoharvest
harvest 432
432 lbs/hr
lbs/hr
(196 kg/hr),
double what
could take.
(196
kg/hr), nearly
nearly double
whatthe
the jet
jet operators could
9.
Growth
the optimum
optimum age
gaper clams
clams
Growthdata
datasuggest
suggestthat
that the
age to
to harvest gaper
in Yaquina
Yaquina Bay
ve years.
Bayisis about
about £i
five
10.
Meat
and
Meatrecovery
recoveryfor
for gaper
gaper clams
clamswas
washighest
highest during
during the
the winter and
averaged 21%
wet weight.
weight.
averaged
21%ofoflive
live wet
11.
Market
Market conditions
conditions more
morethan
than anything
anything else
else affected
affectedthe
thecommercial
commercial
clamming
in Yaquina
Yaquina and
and Coos
Coos bays.
clammingactivity
activity in
12.
Gaper
Oregon, are
Gaperclams,
clams,the
theprincipal
principaltarget
target species
species in
in Oregon,
are not
not easily
easily
marketed. The
The high
bland flavor
highcost
cost of
of processing,
processing, and
and their
their bland
reduces
value as
as a achowder
chowder base
base clam.
clam. Because
few
reduces their
their value
Becauseofofthis,
this, few
Oregon processors
processing gaper
gaper clams.
clams.
Oregon
processorswere
werewilling
willing to
to try processing
13.
Most
Mostofofthe
the gaper
gaper clams
clamstaken
takeninin 1979
1979went
wentinto
intothe
thefish
fish bait
bait
market.
14.
Certain factors
theprofitable
profitableharvest
harvestofofgaper
gaperclams
clams
Certain
factors restricted
restricted the
in Oregon
Oregon from
from 1975
1975 to 1981:
1981:
a.
a.
Harvesting
Harvesting equipment
equipmentwas
wasexpensive
expensivetoto operate
operate and maintain,
maintain,
b.
Labor
were high,
Labor costs
costs were
-14-
c.
c.
Ti-dal
currents restricted the hours/day of effective
Tidal currents
harvest,
d.
d.
in deep
deep water
water which limited
limited down
down
Harvest was conducted in
time for divers,
divers,
e.
e.
proHarvest was
was in
in areas
areas of
of heavy
heavy boat
boat traffic'which
trafficwhich prowaves,
duced dangerous waves,
f.
f.
Visibilities
Visibilities were
were generally poor due to plankton blooms
from river
river runoff,
rtUloff,
or suspended sediments from
g.
g.
The
I-December 31 annually,
annually,
The seaSOnS
seasons were
were short,
short, July 1-December
h.
h.
State
of potenState Board of Health
Health requirements limited areas of
harvest, and in Yaquina Bay,
Bay, allowed
allowed only
only gaper
gaper clams
clams
tial harvest,
taken; and
to be taken;
i.
i.
Processors
and
Processors required a dependable daily supply to hire and
keep crew;
crew; a constant
constant supply could
could not be guaranteed
guaranteed by
by
the harvesters.
Table 11.
11. SlllJlIllary
Summary oJ;
oF Clam Densities
Den~itie~ (No./ft2)
(No./ ft2) in
in. Treatment and
Control Sites,
Site~, Plot C of Area 2,
Bay, 1978-81.
2, Yaquina Bay,
Sample Period
Gaper
Treatment Control
Cockle
Treatment Control
Butter
Treatment Control
Littleneck
Llttleneck
Treatment Control
Macoma
Treatment Control
1978
Spring 1978
6.4
12.6
0,3
0.3
0.0
0.6
0.8
0.3
0.0
14.1
20.6
20,6
Fall
Fall 1978
0.2
12.0
0.3
0.6
0.1
2.0
0.2
1,8
1,8
0.5
48,0
48.0
12.3
6.0
0.3
0.5
0.9
1.0
0.8
0.5
3.3
102.5
0.0
9.6
0.0
0.4
004
3.6
3.5
1.1
0.5
3.7
33,3
33.3
42.0
5.3
1.8
0.3
1.9
1.6
4.1
0.4
5.4
60.3
Fall
1980
Fall 1980
5.1
2.8
0.3
0.2
0,2
3.8
1.0
1.6
0.3
9.3
16.7
1981
Spring 1981
2.6
9.2
0.1
0.2
4,8
4.8
1.3
2.9
0,3
0.3
7.4
24.3
Fall
1981
Fall 1981
1.2
6.1
6,1
0.9
1.5
4.7
5.4
2.8
0.8
4,6
4.6
39.3
39,3
Spring 1979
1979
1979
Fall 1979
Spring 1980
1980
,....,
<n
Ui
I
-16-16-
LITERATURE CITED
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Thomas F.
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and Abalone ProducProducGaumer, Thomas
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to June
June 30,
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Ore. Dept.
13 pp.
pp.
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G. Halstead.
Halstead. 1976.
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Gaumer, Thomas F., and
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1975
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Gaumer,
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September 30,
30, 1980.
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24 pp.
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F., Gregory P.
P. Robart and
and Anne Geiger.
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Clam
Gaumer, Thomas
Thomas F.,
Planting Sites
Sites and
and Effects
Effects of
of Harvest.
Harvest. Comm.
Distribution, Abundance, Planting
Comm.
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September 30,
30, 1979.
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Dept.
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Dept. of Fish and
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47 pp.
Gaumer,
F., and
and Richard
Richard M.
M. Starr.
Starr. 1982. Commercial
Gaumer, Thomas F.,
Commercial Clam Production.
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Act. October 1,
1, 1980 to
to September
September 30,
30, 1981.
1981.
Comm. Fish.
Proc. Rept.
Ore.
Rept. 23
23 pp.
pp.
Ore. Dept.
Dept. of Fish and Wildlife. Proc.
Hancock, D.R.,
D.R., T.
T. F.
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G.B. Willeke, G.P.
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Distribution, Abundance,
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