OREGthI BAY CLAH DISTRIBUTIth, ABU1DAUCE, PLATIUG SITES
A%lD EFFECTS OF HARVEST
AWUAL REPORT
October 1, 1978 to
September 30, 1979
by
Thomas F. Gaunier
Gregory P. Robart
Anne Geiger
Oregon Department of Fish and Wildlife
ational 4arine Fisheries Service
ational Oceanic and Atmospheric Administration
United States Department of Commerce
Commercial Fisheries Research and Development Act
Project Number 1-122-R Segment 3
Contract Jumber 9-M02-ORAC
December, 1979
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CO14TE'4TS
Page No.
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INTRODUCTION
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CL.AMDISTRIBUTIONSTUDIES . . .
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Methods
Location of Suitable Intertidal and Subtidal Clam Planting Site
Results and Discussion
Umpgua Bay . . . . S
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Coos Bay .
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ASSESSMENT OF HARVEST POTENTIAL
Methods
Yacuina Bay
Coos Bay . . . . . . . . .
Results and Discussion
Yaguina Bay
Coos Ba,y
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ResultsandDiscussion ........................
ASSESSMENT OF EFFECTS OF SUBTIDAL CLAM HARVESTING ON SUBSTRATE MATERIAL.
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Methods . . . . . . . . . . .
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Results and Discussion
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Visual Appearance ,
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Sediment Size Analysis . . . . . .
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LABORATORYCLAMSTUDIES
Methods . . . . . . . .
Results and Discussion
Netarts Bay . . . .
Yaguina Bay . . . .
ACKNOWLEDGMENTS
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ASSESSMENT OF EFFECTS OF COMMERCIAL CLAM HARVEST ON RECRUITMENT
Methods
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COMI4ERCIALHARVESTOFCLAMS
Methods
Yaguina Bay . . . .
Coos Bay . . . . . .
Results and Discussion
Yaguina Bay . . . .
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Coos Bay
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15
LITERATURE CITED
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1.5
APPENDIX 1
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Tables
Table No.
1
Page No..
Population and Biomass Estimates of Subtidal Clams in Area 2,
Yaquina Bay, 1979. .
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Summary of Pounds of
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Bay
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Subtidal Clams Harvested in. Coos Bay
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Summary of 4umber'/ of Marine Organisms Occurring in Commercially
Harvested Plot C of Area 2., Yaquina Bay,. Oregon, 1979
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SedIment Sizes Before and After Harvest, Plot C of Area 2, Yaqulna
Bay, Oregon, 1918-79. .
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12
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Percentages of Gravel in the Clam Harvest Area and Results of
Student T-test Comparing Gravel Before and After Harvest, Plot C
of Area 2, Yaquina Bay, Oregon, 1978-79 . . . . . . . S
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Percentages of
Coarse Sand In the Clam Harvest Area and Results of
Student T-test Comparing Coarse Sand Before and After Harvest,
Plot C of Area 2, Yaquina Bay, Oregon, 1979. .
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13
Percentages of Fine Sand In the Clam Harvest Are a and Resul ts of
Student 1-test Comparing Fine Sand Before and After Harvest, Plot C
of Area 2, Yaqulna Bay, Oregon, 1978-79. . . . . . . . . . . . . .
13
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Growth of Butter Clams Planted on the Yaqulna Bay Breakwater,
1979
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Summary of Pounds of Subtidal Clams Harvested in Yaquina
CommercialFishery,1979.
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Population and Biomass Estimates of Subtidal Clams lfl Area 2,
Plot D, Yaquina Bay, Oregon, 1979. . . . . . . . .
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CoimnercialFishery,1979.
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14
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Growth and Survival of Butter Clams Planted In Artiflcia Substrate
Plots, Yaqulna Bay Breakwater, 1968-79 . .
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Figures
Figure No.
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Map of Umpqua Bay Showing Areas Surveyed, 1979
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Gaper Clam Distribution, Umpqua Bay, Oregon, .1979.
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Cockle, Littleneck and Piddock
Oregon, 1979
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CalifornIa Softshell Distribution, Urnpqua.Bay, Oregon, 1919.
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Baltic Clam Distribution, Umpqua Bay, Oregon, 1979
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Clam Distribution, Umpqua Bay,
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Page No.
FIgure No.
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Shrimp Distribution, Umpqua Bay, Oregon, 1979.
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23
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Ecigrass Distribution, limpqua Bay, Oregon, 1979.
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Misc. Plant Distribution1/, Ljmpqua Bay, Oregon, 1979 .
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Map of Coos Bay Showing Areas Surveyed, 1979 .
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Gaper Clam Distribution, Coos Bay, Oregon, 1979
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Cockle Clam Distribution, Coos Bay, Oregon, 1979 .
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Butter Clam Distribution, Coos Bay, Oregon, 1979 .
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Littleneck Clam Distribution, Coos Bay, Oregon, 1979 .
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Softshel1 Distribution, Coos Bay, Oregon, 1979 .
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Macoma Clam Distributlon,J, Coos Bay, Oregon, 1979 .
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Misc. Clam DistributionJ, Coos Bay, Oregon, 1979
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Shrimp Distribution, Coos Bay, Oregon, 1979.
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Eelgrass Distribution, Coos Bay, Oregon, 1979.
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Misc. Plant Distribution/, Coos Bay, Oregon, 1979
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Map of Yaquina Bay, Showing that Area Approved for Comsercial
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Clam Harvesting . . . . . . . . . . . . . . .
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Map of Lower Coos Bay, Showing that Area Approved for Conuiercial
Clam Harvesting . . . . . . . . . . . . . . . . . . . . . . . .
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Year Class Composition of Subtidal Gaper Clams Collected from
Area 2, Yaquina Bay, Oregon, 1979. . . . . . . . . . . . . . .
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36
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Length-Class Composition of Subtidal Gaper Clams Collected
from Area 2, Yaquina Bay, Oregon, 1979 . . . . . . . .
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Mean Size and Weight of Gaper Clams in Area 2 of Yaquina Bay,
Oregon, 1979 . . . . . . . . . . . . . . . . . . . . . . . .
Year Class Composition of Subtidal Gaper Clams from Plot D
of Area 2, Yaquina Bay, Oregon, 1979 . . . . . . . . . . .
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Length-Class Composition of Subtidal Gaper Clams from Plot D
of Area 2, Yaquina Bay, Oregon, 1979 . . . . . . . . . . . .
Year Class Composition of Subtidal Gaper Clams in Coninercial
Harvest, Plot D of Area 2, Yaquina Bay, Oregon, 1979 . . . .
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Length-Class Composition of Subtidal Gaper Clams in Commercial
Harvest, Plot 0 of Area 2, Yaquina Bay, Oregon, 1979 . . . . .
Figure No.
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Page No.
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Year Class Composition of Subtidal Butter Clams tfl.toimuerclal
Harvest, Plot D of Area 2, Yaquina Bay, Oregon, 1979. . . . .
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Length-Class Composition of Subtidal Butter Clams In Conmerc1aI.
Harvest, Plot V of Area 2, Yaqutna Bay, Oregon, 1979 . . .
Year Class Composition of Subtidal Gaper Clams from Connnercta.l
Harvest, Pigeon Point, Coos Bay, Oregon, 1979
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Length-Class Composition of Subtidal Gaper Clams from ConmierçiaL
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Harvest, Pigeon Point, Coos Bay, Oregon, 1979
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Growth Curve of Manila Littleneck Clams Spawned and Planted from
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Normal and Fast Growing Brood Stock in Netarts Bay, 1979. .
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Growth Curve of Manila Littleneck Clams Planted in Fenced, Unfenced
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and Eelgrass Covered Areas of Netarts Bay, 1979 . .
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Growth Curve of Butter Clams Planted on the Yaqulna Bay Breakwater
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(Vertical Lines Indicate Range In mm), 1979 . . . . .
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a
OREGON BAY CLAM DISTRIBUTION, ABUNDANCE, PLANTING SITES AND EFFECTS OF HARVEST
ABSTRACT
We continued our studies of the distribution of bay clams in Oregon's estuaries,
Maps showing the distribution of clams and vegetation type in Iimpqua and Coos bays
are presented.
Population and biomass estimates, age and size of clams were calculated for an
The data revealed that the
area in Yaquina Bay having commercial harvest potential.
1975 year class remained strong for gaper clams. Approximately 3.5 million pounds
(1,570 m.t.) of gapers were estimated for the area and a harvest quota of 200,000
pounds (90.7 m.t.) was established.
During 1979, 74,565 pounds (33.8 m.t.) of clams were harvested in Yaquina Bay.
Of this total, 73,959 pounds (33.5 mt.) or 99.2% were gaper clams; the remainder
were butter clams. Harvesters averaged 593 pounds/hr (269.5 kg/hr).
In Coos Bay 13,901 pounds (6.3 m.t.) of clams were
showed that 286.6 pounds/hr (130.3 kg/hr) were taken.
harvested.
Production figures
Post harvest surveys showed no significant difference in numbers of clam set
settling out in the treatment areas and control sites. Analysis of effects of
harvest on sediment sizes showed, at the 95% confidence level, signiflcantly:blgher
sand
percentages of coarse material in the treatment plot following harvest.
was significantly lower in the harvested area.
fine
We continued to monitor the growth of laboratory produced clams planted in
Netarts and Yaquina bays.
I NTRO0UCTIO
The objectives of this study were: (1) to continue mapping the distribution of
bay clams in Oregon's estuaries, (2) to assess the effects of mechanical harvest on
subtidal claws and habitat, and (3) to evaluate the success of planting hatchery
produced and released juvenile clams in selected Oregon estuaries.
CLAM DISTRIBUTIOfl STUDIES
Surveys
During the year, clam surveys were conducted in Umpqua and Coos bays.
were completed on Vaquina Bay in 1973 (Lukas and Gaumer, 1974), Alsea Bay in 1974
(Gaumer and Lukas, 1975), estucca and Siletz bays in 1975 (Gaumer and Haistead, 1976)
and Tillamook, Wetarts and Salmon River estuaries in 1978 (Gaunier, Robart and Geiger,
1978).
Methods
Location of Suitable Intertidal and Subtidal Clam Planting Sites
We continued to evaluate the distribution of clams using techniques developed
during the 1973 fiscal year (Osis and Gaumer, 1973).
Results and Discussion
Umpqua Bay
Subtidal surveys were initiated in 1979. Surveys were started at the mouth
and extended upbay to the entrance of Salmon Harbor (Figure 1). About 21,000 feet
(6,400 m) of transect were completed.
Six species of clams were recorded (Figures 2 to 5). Gaper and cockle clams
were the principal species observed and occurred primarily in areas containing a
shell, sand and gravel substrate. Shrimp were observed inhabiting much of the
In addition to eelgrass, occassional observations of Viva,,
survey area (Figure 6).
Fucus, Enterornoxpha and brown algae were also recorded (Fi gures 7-9)
Coos Bay
Clam surveys were continued on Coos Bay. To date we have examined 366,100 feet
Figure 9 shows the
(111,587 m) of transect line and have made 1,891 observations.
areas surveyed.
Thirteen species of clams were observed. Of the recreationally or commercially
inortant species, gaper and cockle clams were the principal species observed in
the lower bay and softsheli clams were prevalent in the upper bay. Figures 10 to
16 show the distribution of gaper, cockle, butter, littleneck, softshell, bentnose,
Macoma inqui.nata, M. t.naonspwua, California softshell, bodega, piddock, jackknife
Ghost and mud shrimp distribution is shown in Figure 17.
and rock clams
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a majority (87%) of the gapers in the area. Mean age of the gapers was 4.4 years.
The figure also shows that recruitment is uneven.
In fact, no 1978 year class clams
were observed in the samples. Samples were taken too early in the year to expect
to be recruited into the 1979 year class clam population. Age composition data for
butter, cockle and littleneck clams is not presented due to the small numbers
collected.
The length distribution of gaper clams from Area 2 is shown in Figure 23. Mean
The decrease in mean size might
size was 83.2 mm, a decrease of 7.6 mm since 1978.
be explained by natural mortality of older age-class clams and the strong influence
of the predominant 1975 year class. A mean annual mortality rate of 0.488 was
calculated for gaper clams in Area 2.
It
Figure 24 shows the calculated growth rate of gaper clams taken from Area 2.
required about 5 years to reach the 4 inch (10.1 cm) size acceptable to the processing
The 5-year-old clams averaged 225 grams.
industry.
We estimated that 1.0 million
Population and Biomass Estimates, Area 2, Plot 0.
clams inhabited the 0.4 ha plot of Area 2 (Table 2J. Of this total, 480,000 were
gaper clams weighing an estimated 275,700 pounds (125 m.t.). As with Area 2, the 1975
o clams of the 1976-79 year
year class was the principal age group (Figure 25).
classes were collected in the preharvest sample. Mean age of the gapers was 5.3 years.
Figure 26 shows the length frequency distribution of gaper clams. Mean size
of the clams in the preharvest sample was 100.8 mm which is 17.6 mm larger than for
clams found in the overall Area 2 sample.
Coos Bay
Data
No preseason surveys were made on the subtidal clam stocks in Coos Bay.
collected in 1975 were used to establish a harvest quota of 150,000 pounds (68.0 m.t.)
in 1979.
Table 1.
Species
Population and
Biomass Estimates of Subtidal Clams in
Area 2, Yaquina Bay, 1979.
Number
Irus
11,116,700
16,700
133,300
200,000
10,100,000
Total
21,566,700
Gaper
Cockle
Littleneck
Butter
Biomass (ibs)
3,461,100
2,170
17,382
83,355
Not Determined
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Table 2.
Population and Biomass Estimates of Subtidal Clams in
Area 2, Plot D, Vaquina Bay, Oregon, 1979.
Species
Wumber
Gaper
Littleneck
Butter
480,000
10,000
5,000
545,000
Irus
Biomass (ibs)
275,700
947
3,667
Wot Determined
1,040,000
Total
CO111ERCIAL HARVEST OF CLAMS
In 1979, we issued six permits to commercial clam fishermen to harvest subtidal
Permits were required since the use of mechanical means
clams by mechanical means.
to harvest clams is unlawful. The permits specified the pounds of clams that could
In addition, monthly
be harvested, season, harvest area and harvest equipment.
reports giving pounds and numbers of clams harvested and hours of effort were reQuotas were established by allowing the fishery a maximum
quired of each operator.
of 10% of the available biomass from each respective area. The season started
July 1, 1979, and ended Decener 31, 1979.
Methods
Yaguina Bay
Two commercial clam harvesting permits were issued for the 1979 season. Harvest
A quota of 200,000
was restricted to the 0.4 ha Plot 0 in Yaquina Bay (Figure 20).
pounds (90.7 mt.) was placed on the area which was 10% of the available gaper clam
biomass for Area 2.
Only suction pump harvesters were permitted in the area. Both were diesel
Surface discharge allowed crew
powered with 8-inch (20.3 cm) intake suction tubes.
members to sort clams by size and species. One pump had a discharge of 1,100 gpm
(4163.5 1pm) and the other 800 gpm (3028 1pm).
Each of the permittee's catch was periodically sampled for age, size, weight
and species composition.
Following the 1979 season, we resurveyed that portion of plot 0 that was commerSix 2 ft2 (1.1 m2) samples were taken to determine completeness
cially harvested.
of harvest.
Coos Bay
Four commercial clam harvesting permits were issued for Coos Bay.
held water jet was approved for the removal of clams.
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Only a hand-
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Prior to the start of the 1979 season, the Division of State Lands and the
U.S. Army Corps of Engineers undertook a comprehensive review of their fill and
removal permit systems and their application to the proposed commercial clam fishery.
At their decision, only those people that had previously harvested clams would be
granted conditional approval to harvest in 1979. Because of this, only one of the
four permittees was allowed to remove clams during the 1979 season.
restricted to the Pigeon Point area of Coos Bay (Figure 21).
The fishery was
Results and Discussion
Yaguirsa Bay
The commercial fishery for clams in Plot 0 of Area 2 produced 74,565 pounds
(Table 3).
(33.8 m.t.) of which 73,959 pounds (33.5 m.t.) or 99.2% were gaper clams
through
October
The remainder were butter clams. The fishery extended from August
Each
harvest.
(20.8
rn.t.)
or
61.5%
of
the
total
with August providing 45,824 pounds
593
Harvest
figures
revealed
that
fishing trip averaged 3.5 hours of dive time.
pounds/hour (269.5 kg/hr) or 2,071 pounds/trip (941.4 kg/trip) were taken. The
harvested gaper clams averaged 226.8 gms.
Table 3.
Summary of pounds of Subtidal Clams Harvested in Yaquina
Bay Commercial Fishery, 1979.
Sp.eci es
ftonth
Gapers
Butters
Total
Dive Time
August
175
248
October
45,649
12,489
15,821
183
45,824
12,737
16,004
82.3
23.5
20.0
Total
73,959
606
74,565
125.8
September
The 1975
Figure 27 shows the year-class composition of gaper clams harvested.
Age composition of
frear class was prevalent providing over 67% of the harvest.
estimates.
harvested clams was similar to that of the preseason age
Length-frequency distribution of the gaper clams sampled from the commercial
clams was 101.6 mm as
harvest is shown in Figure 28. 1ean length of harvested
compared to 100.8 mm for the preseason sample.
the commercial harvest is shown
The year class composition of butter clams in class
and the oldest clam aged
in Figure 29. The mode occurred at the 1965 year
was 19 years..
harvested from Plot 0 of
Figure 30 shows the length frequency of butter clams
Area 2. Mean size of clams was 91.7 mm.
about 10% of Pot 0 had
Post harvest sampling of the harvest area revealed that
recovered one Macama clam indicating that the
been worked. In the harvested area we
area had been completely worked out.
-6-
Coos Bay
The commercial clam harvest in Coos Bay produced 13,901 pounds (6.3 m.t.) of
Of this total, 13,351 pounds (6.1 m.t.) or 96% were gaper clams.
clams (Table 4).
Butter and littleneck clams were also taken.
Gaper clams averaged 7.3 years of age with the 1972 year class being prevalent
Divers averaged 4.4 hours of bottom time and produced
in the harvest (Figure 31).
286.6 pounds/hr (130.3 kg/hr) or 1,263.7 pounds/trip (574.4 kg/trip).
The harvested gaper clams averaged 126.4 mm (Figure 32).
harvested from the same area averaged 121.1 mm.
Table 4.
Nonth
In 1978, gapers
Summary of Pounds of Subtidal Clams Harvested in Coos
Bay Commercial Fishery, 1979.
Gapers
Species
Littlenecks
Butters
Total
Dive Time
9.0
October
November
2,607
10,744
39
0
0
511
2,646
11,255
39.5
Total
13,351
39
511
13,901
48.5
The scarcity of 1975 year class gaper clams occurring in the Coos Bay harvest
In
reflects the selectivity of the hand held water jet in size of clams taken.
Vaquina Bay, where the suction pump removed all clams, the 1975 year class comprised
67% of the harvest. Preseason sampling revealed that the 1975 year class was well
represented in each bay.
ASSESSMENT OF EFFECTS OF COMMERCIAL CLAM HARVEST ON RECRUITMENT
One of the major concerns with a new commercial clam fishery is the effects
the harvest might have on future recruitment. Ideally, a portion of the existing
stocks are available for harvest and the remaining clams serve as brood stock capable
of reseeding the harvested areas. One basic objective of our studies was to
determine if the harvested areas were being reseeded by adjacent brood stock.
Methods
The study area was the same portion of Plot C in Area 2 of Yaquina Bay that
Both treatment and control sites
supported the conunercial clam harvest in 1978.
were selected for ease of relocation and in areas of similar sediment and species
composition.
Harvest in Plot C occurred from July through November, 1978. Production was
Approximately 2/3 of Plot C was commercially
153,315 pounds (69.5 m.t.) of clams.
harvested.
-7-
After harvest samples were taken in flarch, May and ovember, 1979. These
samples were taken with a venturi suction pump fitted with a collection basket
covered with 3 mm mesh hardware cloth.
Six 0.2 m2 samples were taken each period in the treatment plots whereas a
single sample, ranging in size from 0.2 m2 to 0.5 m2, was taken each period in the
control plot. The samples were taken 7.6 cm deep which insured all newly set clams
would be collected.
All organisms collected in the screen basket were sorted into groups and
identified to species if possible. All clams were also measured.
Results and Discussion
Clam stocks in both the treatment and control plots were extremely abundant
In 1978 our samples averaged 69.1 gapers,
before harvest (Gaumer, et al. 1978).
3.2 cockles, 3.2 littlenecks, 6.5 butters and 152.3 macoma clams per square meter
in the treatment plot and 329.4 gapers, 16.2 littlenecks, 16.2 butters and 1,944.0
Post harvest samples showed
macoma clams per square meter in the control plot.
only 2.2 gapers per square meter remained in plot C suggesting a nearly complete
removal of clams from the area.
Post-harvest samples revealed that 64 different species of marine organisms
had reestablished themselves In Plot C whereas 46 species were recorded for the
control (Table 5). Mollusca, annelida and arthropoda were all well represented
in the samples.
Of the six, gaper,
Six species of clams were collected from the test plots.
cockle, butter, littleneck and the macoma all have commercial potentfal. A two way
parametric analysis of variance was conducted to test whether harvesting had any
effect on survival of the set of these species of clams. Sources of variation
were partitioned into time, treatments and error. Table 5 shows the F values
calculated for each clam species. There was no significant difference in numbers
of clam set of any species in harvested and unharvested (control) plots. This
suggests that mechanical removal of the substrate through harvesting does not alter
the survival of clams at least in the early stages of life.
ASSESSMENT OF EFFECTS OF SUBTIDAL CLAM HARVESTING ON SUBSTRATE MATERIAL
Methods
We selected a subtidal study area in Plot C of Area 2 (Figure 20) to. determine
The test plot was
the effects of commercial harvest on the substrate composition.
located in 32 feet (9.8 m) of water near permanent surface markers. The area was
selected due to the large abundance of clams and the assurance that the site would
be harvested in the commercial fishery.
Using a subtidal core sampler patterned after one developed by the Washington
Department of Fisheries (Goodwin and Shaul, 1978), five preharvest core samples
Samples
Each core was driven to a depth of 18 inches (45.7 cm).
were collected,
.
ep.
li?ài&zé
Orbiniidae
Opheliidae
Lumbrinereis
Eupo lyrnina creecentis
Glyceridae
Goniadidae
Hapioscoloplos elongatus
Eudistylia
Cistenidee brevicoma
Capitellidae
Cirratulidae
Armandia brevis
Anaitidea willia,nei
ANNELIDA
Parapholas
Pecten
Nassarius mendicus
Nucella
Nudibranchi
Littorina sp,
Mblitussp.
Hermissenda crascicornus
Chiton
Assirninea caUfornica
Anrpnissa
Aeolidia papilloaa
Adula ap.
0.1
0.1
0.1
0.1
0
0
>10.0
>10.0
0
0
0
0
0
0
0
0
0
0.3
0.1
0.2
0
0.4
0
0
0
0
0.1
0
>10.0
>10.0
>10.0
0
0
0
0
0
0.2
0
0
0.6
0
0
0
0
0
0
0.0
0.2
56.6
0.8
2.8
0.0
0
0
0
0
0
0
0
0
0
0
0.0
Tresus capax
Ao,naea ap.
1.2
1.9
Saxidomu8 g1.ganteus
Entodearna saxicola
Macorna inquinata
Venerupis atayninea
0.4
0.0
4.3
Yaquina Bay, Oregon, 1979.
0
>10.0
0
0.3
0
0
0
0
>10.0
>10.0
>10.0
0.5
0
0.1
-
-
0.5
0
0
1.6
1.6
0
>10.0
4.5
0'
2.2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2.0
1.0
0
1.2
0.2
0
0
0.7
0.1
0
0
-
-
-
-
1.7
0.3
4.9
0
0
0
-
0
0
-
0
-
0
-
0
0
2.0
0.6
3.2
1.4
0
0
0.1
-
0
0
0
0
0
0
0
0
0.3
0
0
-
0.1
0.3
0
0
0
2.5
0.5
0.5
-
-
-
-
0
0.2
-
0
0.1
0
-
-
0.3
0
0.1
0.1
0.3
-
-
0
0
0
2.4
7.5
-
4.6
1.3
4.4
0.0
-
8.0
3.8
0.3
0
0.0
-
00
1.0
0.8
0.0
-
0.7
0
0
0
0
0
0
0
0
0
>10.0
>10.0
>10.0
0
3.5
0
0
>10.0
0
1.2
0
0
0
0.5
0.0
102.5
0.5
1.0
6.0
0
0
0
0
0
0
0
0
0
0.3
0.1
0
0
0
0
0
0
12.3
0.1
0.8
0.9
3.3
0.3
0.0
3.0236
5.9406
0.1443
0.7331
0.3309
Summary of umberV of 1arine Organisms Occurring in Commercially Harvested Plot C of Area 2,
Clinocardiwnnuttallii
MOLLUSCA
Table 5.
Continued
0.4
0.1
>10.0
Anthoaoa
anenome
coez.enterata
copepod
crustacean larvae
shrimp
leopod
0.5
0
0
0
0.2
0
0
(lID2! amphi pod
(lID barnacle
(lID
(lID
(lID
(lID
0.1
0
0
0
>10.0
0
0
0
0
0
0.2
0
0
0.1
0
0
0
4.8
>10.0
0.3
0
0.1
0.5
0
0
0.5
1.7
1.9
0
0
0
0
0.3
0
0.2
0
0
0
1.0
0
0
0
>10.0
0
1.8
0.8
0
0
1.6
0.6
0
0
0
0
0
0
0.2
>10.0
0
4.4
0
-
0
1.5
0
0
0
0
0
>10.0
0
0
0
0
0
0
0
0
0. 1
0
0
0.2
0
0
0
0
0
Upogebia pugettensi..s
Hemigrapsus oregonensis
Heptacarpus paludicola
Melita dentata
Paqurus sp.
Petrolisthes
Pinnixa faba
Pyonogonads
ckvmnarid cvnphipods
Cancer productue
Caprellid
Caridean shrimp
Decorator crab
Cancer mag8ter
4RTHROPODA
Balanus 8p.
Nerisap.
UID Worm
Terebellidcze
tJID Flatworm
Polynoidas
Scale worm
Serpulid
Sipunculid
Spionidae
Polycl1adia
Table 5.
-
0.5
0
0
0
0
0
0
>10.0
0
0.5
0
0
0
0
0.5
0
>10.0
2.0
0
1.5
0
0
2.0
0
0
0
0
1.0
0.5
0
0
0
1.8
0,2
1.0
0
0
0
0.1
0
0
0.1
1.0
0
0.7
0
1.4
0
0.2
0
0.1
>10.0
0
0.5
0.2
0
0
2.7
0
0
3.2
0
0
0.2
0
0
0
-
0
0
0.1
0
1.3
0.5
0
0
0.2
0
0.1
-
-
-
-
-
-
-
-
-
-
-
-
-
1.8
0
0
0
0
0
0
0
0
0
2.9
-
-
-
-
-
-
-
0.5
0.2
0
0
0
0.8
0.1
-
-
0
0
0
0
0
0
0
2.8
0
0
0
0
0
0
0
0
'0
0
0
0
0.8
0
0
0
0
0
0
0
0
0
0
0
4
Continued
!umbers are organisms/ft2
Unidentified organisms
1/
2/
PORIFERA
Sculpin
Gunnel
VERTEBRATA
TUNICATA
Tux*beilarian
Polyclad
PEA TYIiELMIN2 WES
Zt7emertea
Echiuroidea
(irechis caupo
Pyonopodia helianthoide
Ophiuroidea
PisaBter ochraceus
Euasteria troBoheill,
Echinodermata
Tabk 5.
0
0
0
0
0
0
0
0
0
0
1.0
>10.0
0
0.6
0
1.6
0
0
0
0.4
0
0
0
0.6
0.3
0
0
0
0
0
-
0
0
0
0.2
0.5
0
0
0
0.3
0
0.3
0
0.8
0.2
0.1
-
0.4
1.0
0.5
0
-
0
0
0
0
-
0
3.4
-
2.7
0.1
0.3
-
-
-
0
0
3.6
0
2.7
0
0
0
0
0
0.3
-
0
0
2.3
-
0
2.7
0.5
0
3.0
0
0
0
1.6
0
1.4
0.3
0.8
.
4
9
-11-
were carried to the surface, removed from the corer, placed in plastic containers and
fixed with 10% forrnalin for transport to the laboratory. Following the commercial
harvest, five additional sediment samples were taken from the same vicinity as the
preharvest samples. Sampling methods were exactly the same.
In the laboratory, sediment size was analyzed with the following sieve techniques:
Sieve sizes used were as follows:
>1.651 mm; gravel
0.850 to 1.651 mm; very coarse sand
0.420 to 0.850 mm; coarse sand
0.246 to 0.420 mm; medium sand
0.125 to 0.246 mm; fine sand
0.063 to 0.125 mm; very fine sand
0.0045 to 0.063 mm; silt
Suspended silt was
Each sample was first washed with distilled fresh water.
removed using a Millipore filtering device (0.45
paper filter) and a water powered
venturi suction pump. This filtrate and all other substrate material were dried in
an oven at 50° C overnight. Once dried, the material was placed in a stack of Tyler
sieves and put onto a Rotap sieve shaker for 15 minutes.
Each sieve pan was emptied
and contents weighed on a tiettler balance to the nearest gram.
One before-harvest and post-harvest sample was saved and photographed for
comparative purposes.
Results and Discussion
Visual Appearance
Following the commercial harvest, our divers returned to the area to see if visual
changes had occurred. Although subjective, these observations showed that tidal
No obvious pits or other
currents had removed most evidence of the prior fishery.
On the surface, there
irregular configurations in bottom contour were detected.
appeared to be slightly more shell following the harvest. One obvious change was the
scarcity of adult clams in the harvest area.
Sediment Size Analysis
Vaquina Bay subtidal sediments in Area 2 were primarily composed of sands and
Pre and post harvest
shell, a characteristic common to subtidal clam bed habitat.
samples showed that percentage of coarse materials were generally higher in the post
harvest samples (Table 6). Percentages of both the gravel, shell and coarse sand
were significantly higher at the 95% confidence level following harvest whereas the
percentage of fine sands was significantly lower. Only the fine silt showed a slight
increase following harvest. These data suggest that a certain percentage of the fine
sand was carried from the area of harvest to adjacent areas. Fine silt appeared to
Unfortunately, no control samples were
be redeposited back in th harvest area.
Tables 7, 8, and 9 show
taken in adjacent areas to substantiate this hypothesis.
the statistics for those samples having significant differences. Arc sine transformation was applied to the data because the data were precentages.
-12-
Table 6.
Sediment Sizes Before and After Harvest, Plot C of Area 2,
Yaquina Bay, Oregon, 1978-79.
Percent retained on various size sieve openings.
Sieve openings in microns.
Core/Sieve size
1651
850
49
1.5
2.3
5
17.0
3.9
7.4
5.1
x
6.9
1
2
3
4
246
420
Before Harvest
125
63
<63
16.9
12.3
16.5
17.0
18.6
68.0
58.8
69.2
67.2
66.5
3.4
3.4
3.5
2.7
2.8
2.7
1.7
1.0
2.6
3.4
2.6
2.4
1.7
2.8
4.0
1.5
1.5
2.5
16.6
66.5
3.4
2.6
15
3.3
After Harvest
2
3
16.2
11.8
16.2
4
20.3
5
15.9
3.3
2.2
2.1
2.8
2.2
16.2*
2.5
1
*
3.6
3.0
3.6
3.7
3.6
17.7
13.2
14.5
16.9
16.8
53.4
63.6
57.8
50.1
54.3
3.3
3.0
3.2
3.0
2.6
4.5
3.2
2.5
3.2
4.6
3,5*
15.8
554** 3.0
3.6
Significant at the 95% confidence level.
Significant at the 99% confidence level.
**
Table 7.
Core #
Percentages of Gravel in the Clam Harvest Area and Results of
Student T-test Comparing Gravel Before and After Harvest, Plot C
of Area 2, Yaquina Bay, Oregon, 1978-79.
Before Harvest
Arc Sin
Percent
1
4.9
2
3
4
5
17.0
3.9
7.4
5.1
12.79
24.35
11.39
15.79
13.05
After Harvest
Arc Sin
Percent
16.2
11.8
16.2
20.3
15.9
23.73
20.09
23.73
26.78
23.50
2357
Mean after harvest
Mean before harvest =
harvest
= 5.62
after
Variance
Variance before harvest = 27.16
harvest
= 2.37
Std.
0ev.
after
Std. 0ev. before harvest = 5.2
4.83
F Value
3.16*
T Value
Degrees of freedom 8
* Significant at the 95% confidence level.
-13-
Table 8.
Percentages of Coarse Sand in the Clam Harvest Area and Results
of Student 1-test Comparing Coarse Sand Before and After Harvest,
Plot C of Area 2, Yaquina Bay, Oregon, 1979.
After Harvest
Percent
Arc Sin
Before Harvest
Percent
Arc Sin
Core #
2.6
3.4
2.6
2.4
1.7
1
2
3
4
5
9.28
3.6
3.0
3,6
3.7
3.6
10.63
9.28
8.91
7.49
10.94
9.98
10.94
11.09
10.94
ilean before harvest = 9.12
Mean after harvest = 10.78
Variance before harvest = 1.26
Variance after harvest = 0.20
Std Dcv. before harvest = 1.12
Std 0ev. after harvest = 0.45
F Value = 6.30
T Value = 3.07*
Degrees of freedom = 8
* Significant at the 95% confidence level.
Table 9.
Percentages of Fine Sand in the Clam Harvest Area and Results
of Student 1-test Comparing Fine Sand Before and After Harvest,
Plot C of Area 2, Yaquina Bay, Oregon, 1978-79.
Core #
1
2
3
4
5
After Harvest
Arc Sin
Percent
Before Harvest
Percent
Arc Sin
68.0
58.8
69.2
67.2
66.5
Mean before harvest = 54.32
Variance before harvest = 6.02
Std 0ev. before harvest = 2.45
F Value = 1.47
53.4
63.6
57.8
50.1
54.3
55.55
50.07
56.29
55.06
54.63
46.95
52.89
49.49
45.06
47.47
Mean after harvest = 48.37
Variance after harvest = 8.87
Std Dev. after harvest = 2.98
I Value = _345*
Degrees of freedom = 8
* Significant at the 99% confidence level.
-14-
LABORATORY CLAM STUDIES
Since then we have annually
Our laboratory clam studies were terminated in 1975.
monitored the growth of clams planted in !etarts and Yaquina bays.
Methods
Two studies were continued in Ietarts Bay. One compared the growth characteristics
of Manila littleneck clams that were selected for their fast growing ability vs.
normal growing clams (Gaumer and Lukas, 1975); the other compared growth of clams in
a screened enclosure vs. unscreened areas.
The only study continued in Yaquina Bay compared the growth and survival of butter
clams planted in a natural substrate vs. artificial substrate (Lukas, 1972).
Results and Discussion
Ne tarts Bay
Manila littleneck clams spawned in August 1974 from fast growing parent stock
grew 1.7 mm since June 1978 and averaged 36.9 mm in length, whereas progeny from the
flnormalH clams grew 1.8 mm and averaged 34.1 mm (Figure 33). We have been unable
to determine survival of the Manila clams due to their movement outside the study
plot.
Manila clams planted in the screened test plot averaged 36.0 mm, an increase of
1.1 mm since 1978, whereas clams planted in an adjacent unscreened test plot averaged
37.5 mm, an increase of 1.9 mm since 1978. Manilas planted adjacent to an eelgrass
bed and at a slightly lower elevation were 42.9 mm, an increase of .5 mm since 1978
(Figure 34). Clams in all three plots averaged 13.1 mm when released.
Yactuina Bay
Butter clams sampled from the natural substrate averaged 64.9 mm, an increase
of 2.0 mm since July 1978 (Table 10). These clams averaged 20.0 mm when planted in
1970 as 22-month-old clams.
Table 10.
Growth of Butter Clams Planted on the Yaquina Bay Breakwater,
1979.
*
Date
Sampled
Mean Shell
Length (mm)
7-13-72
7-30-73
7-19-74
7-9-75
7-27-76
8-2-77
7-20-78
7-23-79
37.0
46.7
48.4
53.7
60.0
65.4
62.9
64.9
(months)
Months
in Plot
44.5
57.0
68.0
80.0
92.0
105.0
116.0
128.0
22.0
34.5
46.0
58.0
70.0
83.0
94.0
106.0
Age of Clams
-15-
*
We discontinued calculating survival of butter clams in the natural plot due to
difficulties encountered in dlfferent7atrng between natural set clams and laboratory
planted clams
Growth and survival of butter clams planted in artificial substrate test plots
is shown in Table 11. Our sampling in April 1979, 124 months after the clams were
planted, showed a survival ranging from 0% (for clams planted in natural substrate
and 1.9 mm minus crushed rock) to 0 8% for clams planted in both 19 mm minus crushed
rock and in crushed rock 38 mm to 7u mm.
Where survival occurred, growth of the butter clams was generally similar for
An unexplained phenomenon in 1979 was the decrease in mean
each type of substrate
No apparent mortality of larger
size for each group of clams since the 1978 samples
Figure
35
compared
the
growth
rate of butter clams planted
size clams was observed
artificial
substrates
in natural substrate material vs
ACKN0WLEDGME4TS
We wish to thank Laimons Osis and Darrell Demory of the Department of Fish and
Wildlife, Dave Bernard of Oregon State University and Marian Asche for their assistance
in the study.
LITERATURE CITEE)
Methods of Supplementing Clam and
1976
Gaumer, Thomas F. and Bruce G. Haistead
July 1, 1975 to June 30,
Comm Fish Res and Devel Act
Abalone Production
Ore Dept of Fish and Wildlife Proc Rept 65 pp
1976
alethods of Supplementing Clam and Abalone
1975
Gaumer, Thomas F. and Gerald Lukas
July 1, 1974 to June 30, 1975.
Production. Comm Fish. Res and Devel Act
Fish Comm of Ore Proc Rept 34 pp
1978. Oregon Bay Clam
Gaumer, Thomas F , Gregory P. Robart and Anne Geiger
Comm Fish Res.
Distribution, Abundance, Planting Sites and Effects of Harvest
Ore. Dept of Fish and
October 1, 1977 to September 30, 1978
and Devel Act
Wildlife Proc Rept 65 pp.
Distribution and Abundance of Subtidal Hard-shell Clams in Puget
1973
Goodwin, C L.
14
81 pp
Wash Dept of Fish Tech. Rept. No
Sound, Washington
Some Effects of the 1echanical Escalator Shell1978
Goodwin, Lynn and Warren Shaul
fish Harvester on a Subtidal Clam Bed in Puget Sound, Washington. Wash Dept. of
Fish. Prog Rept No 6. 23 pp.
Comm Fish. Res. and Devel
Clam-Abalone Spawning and Rearing
1972
Lukas, Gerald
of
Ore.
Proc Rept 16 pp.
Fish
Comm
July 1, 1971 to June 30, 1972.
Act
Lukas, Gerald and Thomas F. Gaumer.
Comm. Fis'i
Feasibility Study
Fish Corn, of Ore. Proc
1974
Clam-Abalone Stock Supplementation
1974.
July 1, 1973 to June 30,
Res and Devel. Act
Rept
20 pp
Clam
Estuary Resource Survey, Subtitle
1973
Osis, Laimons and Thomas F Gaumer
Completion
Rept.
Corn. Fish. Res. and Devel. Act.
Inventory Techniques Study.
Fish Comm of Ore. Proc Rept. 11 pp.
July 1, 1971 to June 30, 1973
I-
.
12/15/68
6/8/69
12/26/69
3/25/70
12/9/70
4/12/73
12/15/68
6/8/69
River Run
19mm
Crushed
19mm -
.,.
12/15/68
6/8/69
12/26/69
3/25/70
12/9/70
4/12/73
4/25/74
4/28/75
4/16/76
4/6/77
4/25/78
4/30/79
Crushed rock
19mm to 38mm
.
12/15/68
6/8/69
12/26/69
Control
4f25/78
4/30/79
124
1O
112
88
76
..
4.5
0.8
0.8
1.6
1.1
3.4
2.4
1.7
1.0
4.5
100.0
6
12
15
24
52
64
0.0
0.5
0.2
0.0
100.0
1.0
0
24
52
15
0
6
12
100
112
124
88
76
52
64
24
15
3.3
0.0
2.0
0.8
0.1
0.1
0.1
0.1
0.1
0.1
0.1
.100.0
'
.
72.7
72.2
6. I
23.8
38.8
61.2
62.2
64 7
65.6
20.8
2.9
10.5
-
23.8
41.0
-
2.9
7.9
24.4
38.6
56.1
59.1
63.0
64.9
71.4
72.1
71.5
-
2.9
10.3
-
0.0
12
0
6
12
2.9
11.1
--
Mean
size (mm)
100.0
1.5
(%)
Survival
0
6
..
Months after
release
477 .,.
4/12/73
4/25/74
4/28/75
4/16/76
12/9/70
12/26/69
3/25/70
Date
sampled
.
4
V
.
Crushed
38mm to 76mm
River Run
19mm to 38mm
Substrate
type
.,
4/12/73
4/25/74
4/28/75
4/16/76
4/6/77
4/25/78
4/30/79
12/15/68
6/8/69
12/26/69
3/25/70
12/9/70
12/15/68
6/8/69
12/26/69
3/25.70
12/9/70
4/12/73
4/25/74
4/28/75
4/16/76
4/6177
4/25/78
4/30/79
100
112
124
88
76
52
64
6
12
15
24
0
52
64
76
88
100
112
124
12
15
24
0
6
Date Months after
release
sampled
.
0.9
0.9
0.9
0.8
1.7
1.4
1.3
1.5
2.4
2.5
100.0
7.3
-
365
0.7
0.2
0.3
0.3
0.3
0.3
0.3
0.3
63.6
69.1
71.7
69.9
2.9
9.2
19.6
22.2
38.2
49.9 1972
58.5
60.3
62.3
67.0
71.8
67.9
-
61.0
63.2
65.3
2.9
7.4
20.7
23.3
.
-Mean
size (imi)
100.0
0.8
1.8
0.9
(%)
Survival
Growth 'and Survival Of Butter Clams Planted in Artificial Substrate Plots, Yaquina Bay
Breakwater, 1968-79.
Substrate
type
Table 11.
p
-18-
I
I
/
4
I
I
I
a
ARMY
I
/
S
.1
I
I
I
I
I
1
Figure 1.
Map of Umpqua Bay Showing Areas Surveyed, 1979.
'1
- 19-
/
'I
II
ARMY
HILL '
/
I
Figure 2.
Gaper Clam Distribution, Umpqua Bay, Oregon, 1979.
ARMY
4
HiLL /
r
'
/
7:
/
I
Figure 3.
Cockle, Littleneck and Piddock Clam Distribution, Umpqua Bay,
Oregon, 1979
-21-
'1
I!
I,
Ii
ARMY
I
'1
I'
VI
I.!
I
I)/
I:)
Is
1/
I
Figure 4
HILL
:,'
//
/
California Softshell Dlstrlbutèon, lJmpqua Bay, Oregon, 1979
:
-22-
I
I
I
I
I.
I.
ARMY
I
I,
HILL
1.
jr
/
Figure 5.
-
Baltic Clam Distribution, Umpqua Bay, Oregon, 1979.
>..-.:.....
7
7
-23-
I
ARMY
a
Figure 6.
Shrimp Distribution, Umpqua Bay, Oregon, 1979.
-24-
,1
ARMY
H'LL
I,
/
I
I
II
11
/
(c'
jfl
I
I
I
I
lj
I,
1"
(
1
I
1'
I'
(
1/
I)
r
If
/
S
I'
I
I,
If
r
1.
s:sJ
dIVS
"V
/
Figure 7.
.M
Eelgrass Distribution, Umpqua Bay, Oregon, 1979.
. 1j 4'JJ
-25-
).
ARMY
HiLL
7///)
.fl,
Figure 8
J
Misc
Includes
Plant Distribution1!, Umpqua Bay, Oregon, 1979
Ulva, Fucus, Enteromorpha and brown algae
21/7
21>
25
_/34
36
I
o
/jlI
/
flunt HOt'-
/
/
)
7
Ap.t
I
1'
24
'9
2
30
t26
F
60N
3
a
Crieccv-
P t(41
/
C rrPr.
I
I
1!
/
ecton Cortw'r
I"ojeced Correr
I
14
Figure 9
r
lChII(J
WflPr
f1.
wP( r
t WI
II
M>in
Map of Coos Bay Showing Areas Surveyed, 1979
p
27
/
'V
I
I
16
0
/
> ç'
/
ç
--
J,/ 4/'#
20
22
78
29
/
jy
-
34
34
/JE'7
i
L4 tiLi
ii
S CtO44./(4
> S C4.M4$ /.Q,
u
Sclion Corners Luctci I'
Oee Souices
Secx,n Cornen Fnd
-
P'ü.ct,d Coinsr
1idSknd 8twn Emcr' of Mean La.
ad Mcon I4çi Wav
Wvt*i
()Q(r
\
'!;
Figure 10
Gaper Clam Distribution, Coos Bay, Oregon, 1979.
3
3.
-28
/
4,
,, O.7
V
/
///4
c-I
0
4fl*';
5
/
4
C
-c-I
1
/
),
)
,
/
I
4
4;!-
I
(J
J.
7
43
/
1
o,
'4 4
/
4
/
/
24
20
_..
/i.
30
1
I
1..
'l
Jilt
W',kP
j
"I
Lo
(-5
Le
k
cc.s /4t
>.
-..
I#l,
I(
l
(r'5 L
Seton Co(ref
g
Futd
Pvo,ectc.i Co'e
T,jtk4 R,*epi
(I
4')
v
#.c (f Mq.-)n
ord Mvn Il?h Wur
j:
Figure 11.
Cockle Clam
Distribution,
Coos
Bay, Oregon, 1979.
-29
/
+
6
/
I
24
/
p1/
20
2t
2?
1'
2R
>
I,
//
I?
: :
ID?
)
ç.
/
Loc1 Iron Oth
Prr,.c.6 Cor
Tdsbd 8e$wo
I st.cns of Mei L.ou
Wet and Møn Hqh Waist
.rt.
Figure 12.
Butter Clam Distribution, Coos Bay, Oregon, 1979.
-----.----...-- .- ----.- . ----=---------------,----
:i\
/
/
/
/
/
'''
.,.)
/
/
/
I
'e
i
/
I
/
)
PJU
1)
I
V
("
E
:
20
24
/,/I
/
jI
,
22
2
/
30
29
't,:)
,//'
.
36
3
s:,,
O'k Sk&Lt
.
L.\
/'
IJ?
c'
I
j ,)
,)
1
Cones Lnr1 r,(fl, 0*
SecIu CWnSI
PPCI*d c','sr*
Ttsk4 8s4w.*
/
fl
j, '
L
Figure 13.
3
4 Mn
t01('!i
FIsvotcin ol L4Ia
II
Hi,1
Littleneck Clam Distribution, Coos Bay, Oregon, 1979.
28
26
J
A)
/
f44Ø
Jo'd
Cçye
4i
6
'
45
5
JIi
'
&
1
//
J
I
r'
f
/
/
o'sS
I
A..pwI
}
4
/
1
/
(
/
/
/
20
24
'
tt
/
28
29
/1 )
.,
34
3
i
Ltt
iL
tou,¼ 5%
Li (
t.#d:
,.
-
-,
d
/
,--)
/
Figure 14.
(-5 c\o.e/
5 45/(4 '
A
Seci
Corners Locacd Frvn 011w Sourq,
S.chcwl Cners tout9
Pm.c'sd Come's
1 dekyd Between
Wale,
d Menn
pt,
tow
t-bqt, Watm
Softshell Distribution, Coos Bay , Oregon, 1979.
-
-
.....-,, .- --. -...-.
.-.. -
/
.t.
'
//
I
r- xs; 2
d\ '4.1
JL,4 IL-'9
3;
1
/
C,
+
/
,
I
4:
4
3O
e
28
29
21
(T(.r-)
34
>
I-,.
SeIor Coers LcCud Fon Oer So,it
S,cIn Cc,tws Found
Pwc'w Con
fri
1
%
Figure 15.
J
.--
Ttsb4 8i'wen (%4MJhc$
Mson
Macoma Clam DistributionJ, Coos Bay, Oregon, 1979
mci udes M200ma nasuta M. inquinata and M. inconopicua.
p
T
2 q
8
32
33
c
/
I
/
(1
/6
0
4
1
/
;
I
//
(J
+
r.,*, 8.'d
k
tAi
¼
/
1
I
()
I'
I
/
5
j*ti)
/
(
/
/
/r
I..
24
a
2
F,'
/
/
.I7
28
.1
4':/
.
i7Tç(J1
I'
Leev'ci
',n.,
-
(
71
Ltt4r
v
&e
V
-
c\o
J(4
>5
II
)Sect
J
)
S(
x-cd Ir(,m Ote
c
Projicted Co're's
Titord R,t*c
-
Figure 16.
Cers
Seciort Cov,cs 1jr,d
q'
Misc. Clam
FJ-o.'s of Mrv
Wtjteq ond M'r H.i Wntev
i
4
Distribution'!,
Coos Bay,
Oregon, 1979.
Includes Calif. softshell,bodega, piddock, jackknife and rock clams.
-_-,_
41
5
0
\
/
1/
/\
)
-.
,r
(
)
IØ'd
4,
.)I
/
/
,;
'.
U3
-H
//
./
2
/
::'
28
27
/
Le
c
5AA-
-J ./
i...,
2
I,,-"'
\,
7/
;ç'
,,
P( H>1
I f'er%
L
-:7
)
J/
Figure 18.
-
(,
P,ueced Cov*
Y.<$Qfld
Wcjter
-
$ ?y! Ctq
,-,
1
/'/#
1
ty
4IW1fl
M
I OW
M.cjn
Eelgrass Distribution, Coos Bay, Oregon, 1979.
--
33
/
C
4\._)
h
/\
¼
/
/
I
J
,1
frI
fl
d"
3
(t:j
/t
l
/
/
16
'4
\c)
-37-
4
L
Figure 20.
Map of Yaquina Bay, Showing that Area Approved for Comercial Clam Harvesting.
1
*
r
/.
*
I
1'EON T-INT
ARVIEW
Coos87
a
Figure 21.
82
/500
z000
4600
O0Oflt'T
Map of Lower Coos Bay, Showing that Area Approved for
Commercial Clam Harvesting.
4
30
20
S.ci
cL
0
50
10
60
70
80
90
100 110
120
130 140
150
160
Length-Class (mm)
Figure 23.
Length-Class Composition of Subtidal Gaper Clams Collected
from Area 2 Yaquina Bay, Oregon, 1979.
80
70
60
I0
1979
78
77
76
75
74
73
72
71
70
69
68
67
Year Class
Figure 22.
Year Class Composition of Subtidal Gaper Clams Collected
from Area 2, Yaquina Bay, Oregon, 1979.
-40-
20
10
w
43
cii
U
U
Length-C'ass (mm)
20
4)
10
0
0
10
20
30
40
50
60
70
80
90
100
110
120
Length-Class (mm)
Figure 30.
Length-Class Composition of Subtidal Butter Clams in
Commercial Harvest, Plot D of Area 2, Yaquina Bay,
Oregon, 1979.
30-
N=122
20
a)
4-)
C
w
C-)
ci
age = 13.1 years
V
20
10
C
Cl,
C.,
U
0
I
z
w
J
I
Figure 33.
3o
30
40
50
_--3
60
AGE (MONTHS AFTER RELEASE)
20
:
70
Growth Curve of Manila Littleneck Clams Spawned and Planted from Normal and Fast
Growing Brood Stock in Netarts Bay, 1979.
10
- tTt
p
U,
I
-46-
ii:
iri
U)
aO
'gl
c
(u
UJ
f*.
'c,
-o
(lJ
(u
o
t+-
tO *"
(,13
L^rJ
;L}O
<t
m
w
afl
trZtd
19tdt)
Jt!-z
hJ Z trj
L&! 3 li-
(u
o
a
Ll-
A [rJ
ri"} J
k-l
!
(u
+)
tl-
\
(Y
\
-(f
3 r.d
tn
E
(J
\
Li-
Ol
-52 r\
C)OI
c)d
g
(u
-)
ow
nDg
F,-
z
c)
\
()E
c$
JA
P
(dL
r(6
.r *)
c(u
c6 Z.
E r.l-
(Fo
o
iid'
tn
qJ.d
ill-l
CJ
(5
4t
I
+t rtt
+, co
>(u
LL
=<
!
EA
{J 5=aJ
o>
5,O
ct (J
+
'r\'
\':
cf)
(u
L
5
\.
o
cf
o
ff)
(-,
.{
I
tl-
(urtu) HIgNSl
I
!
tt:
?
k
s
.1
/
35.
10
0
40
60
70
90
90
AGE (MONTHS)
50
100
110
120
±1---
130
1
140
Growth Curve
of Butter Clams Planted on the Yaquina Bay Breakwater (Vertical
Lines Indicate Range in nm), 1979
20
I
T1 ji !Jl
CLAMS PLANTED
/1,"i
/
1-CLAMS PLANTED
Figure
lob
20
O4
z
w
5o
6O
70
-
ARTIFICiAL SUBSTRATE PLOT