FRI-UW-8612
December 1986
Dungeness Crab, Cancer maqister, Distribution
Recruitment, Growth, and Habitat Use
in Lummi Bay, Washington
by
Paul A. Dinnel, David A. Armstrong, and Russell 0. McMillan
December 1986
for
Lummi Indian Tribe, Bellingham, Washington
In cooperation with Washington Sea Grant, Puget Sound Office
of the U.S. Environmental Protection Agency, Washington
Department of Fisheries and Shorelands Division of
Washington Department of Ecology
'
UNIVERSITY OF WASHINGTON
SCHOOL OF FISHERIES
_ FISHERIES RESEARCH INSTITUTE
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FRI-UW—8612
December 1986
Dungeness Crab, Cancer magister, Distribution
Recruitment, Growth, and Habitat Use
In Lummi Bay, Washington
Paul A. Dinnel, David A. Armstrong, and Russell 0. McMillan
Fisheries Research Institute
School of Fisheries
University of Washington
Final Report
December 1986
Lummi Indian Tribe, Bellingham, Washington
In cooperation with Washington Sea Grant, Puget Sound Office
of the U.S. Environmental Protection Agency, Washington
Department of Fisheries and Shorelands Division of
Washington Department of Ecology
, rector
by
for
Approved:
Submi tted Dec. 15, 1986
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A study of Dungeness crab, Cancer magister distribution, recruitment,
growth and habitat preferences was conducted in Lummi Bay, Washington from
July 1984 to September 1985. During this period, Dungeness crab were
sampled at 13 stations with a small beam trawl; sampled at 4 stations with
commercial-style crab pots modified with small-mesh screen to retain small
2
crabs; and sampled intertidally with 0.25m quadrat samples dug at low
tide. The primary objective of this study was the collection of Dungeness
crab distribution data in the area of a proposed navigation channel to be
dredged across the intertidal flats to a new marina.
Average abundances of crabs in the beam trawls were highest during the
summer months (up to 969 + 414 crab/ha) and lowest during the winter (as
low as 1 + 1 crab/ha). Crab catches in the trawls were generally highest
at the -3 m (below MLLW) contour along the nearshore "dropoff" and least
abundant offshore at the -12 m contour. The average sizes of crab caught
in the trawls was also a function of depth with the smallest crab being
caught in the intertidal areas and the largest crab at the -12 m contour.
Abundances of Dungeness crab in the crab pots followed the same
pattern as in the trawls: high during summer, low during winter. The
highest average catches and smallest crab were from the inner portions of
the north channel.
The intertidal quadrat sampling caught young-of-the-year (YOY) crabs
almost exclusively. Settlement of new recruits started in July, peaked in
August and continued through September. Average densities of new recruits
'2
in the eel grass beds reached as high as almost 20 crab/m during August
1986 but declined in each year to average densities of only about 1 to 3
2
crab/m during the winter. The average overwintering size of the YOY was
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in the range of 10 to 20 mm. Growth during the second year was rapid with
crabs reaching 80-100 mm by winter of the year following settlement. Y0Y
crabs were highly associated with any type or plant material in the
intertidal areas of Lummi Bay; very few young crab were found where
protective cover was lacking.
Dungeness crab exhibited preferences for certain habitats by age
group. The Y0Y crabs (up to about 30 mm size) thrived in the intertidal
eel grass/algae areas. One-year-old crab moved off of the flats in about
July and were predominately caught in the shallow channels and along the
nearshore "dropoff" at -3 m depth. The two-year-old crabs also moved deeper
during the summer to the -12 m depth and deeper. Hence, there is a
stratification of crab sizes (age groups) by habitat type (depth) with
minimal overlapping in time or space.
The potential impacts of channel dredging on Dungeness crab are
discussed with recommendations given for monitoring the impacts of the
dredging activity.
ii
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TABLE OF CONTENTS
Page
LIST OF FIGURES v
LIST OF TABLES vii
ACKNOWLEDGEMENTS viii
INTRODUCTION 1
MATERIALS AND METHODS 4
Sample Methods 4
Beam Trawls 5
Crab Pots . . 5
Intertidal Quadrat Sampling 7
Sample Sites ... 7
Beam Trawls 7
Crab Pots 9
Intertidal Quadrat Sampling 9
Data Analysis 11
RESULTS 12
Beam Trawls 12
Crab Pots 25
Intertidal Quadrat Sampling 28
DISCUSSION 40
Potential Impacts of the Proposed Navigation Channel 46
Short Term Effects 46
Long Term Effects 52
RECOMMENDATIONS 54
General Recommendations 54
Project-Specific Recommendations 55
iii
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Page
LITERATURE CITED 56
APPENDIX. 58
iv
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LIST OF FIGURES
No. Page
1. Map of western Washington State showing the location of
Lummi Bay 2
2. Project location map of the proposed Lummi Bay marina
(from COE 1983) 3
3. Diagram of the 3 m beam trawl used to assess crab resources
in Lummi Bay 6
4. Locations of beam trawl stations in Lummi Bay 8
5. Locations of crab pot stations in the north and middle
channels and the intertidal transects in north, middle
and south Lummi Bay .. 10
6. Average estimated abundances of Dungeness crab calculated
from beam trawl catches in Lummi Bay from July 1984 to
October 1985 14
7. Average carapace widths (+ 1 standard deviation) of
Dungeness crab caught by Feam trawl in Lummi Bay from
July 1984 to September 1985 18
8. Size-frequency histograms of Dungeness crab caught in the
beam trawl for each sample month, all stations combined 19
9. Size-frequency histograms of Dungeness crab caught in the
beam trawls in four areas of Lummi Bay (stratified by
depth), all sample months combined 21
10. Top: Average beam trawl tow speed and volume of substrate
material caught in the trawl at each Lummi Bay trawl station.
Bottom: Breakdown by category of substrate materials caught
in the beam trawl for each set of stations, stratified by
depth 24
11. Air and water temperatures from stations 7 (intertidal),
8 (-3 m) and 9 (-12 m) in Lummi Bay from December 1984
to October 1985 26
12. Surface and bottom water salinities from stations 7
(intertidal), 8 (-3 m) and 9 (-12 m) in Lummi Bay from
December 1984 to October 1985 27
13. Average catches (+_ 1 standard error) of Dungeness crab in
crab pots set at four stations in Lummi Bay from August
1984 to September 1985 29
14. Average carapace widths (+ 1 standard deviation) of
Dungeness crab caught in crab pots in Lummi Bay from
October 1984 to September 1985 30
v
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No. Page
15. Size-frequency histograms of Dungeness crab caught in the
Vexar-modified crab pots by sample month, all stations
combined 31
16. Size-frequency histograms of Dungeness crab caught in the
Vexar-modified crab pots set at each crab pot station in Lummi
Bay, all sample months combined....... 33
17. Average (+_ standard error) densities of juvenile
Dungeness crab from July 1984 to October 1985, all
intertidal transects combined 35
18. Average densities of juvenile Dungeness crab for intertidal
Transects 1, 2 and 3, July 1984 to October 1985 35
19. Size-frequency histograms of Dungeness crab caught in the
intertidal quadrat samples along three transects in Lummi
Bay, all transects and stations combined by month 36
20. Average densities of 0+ and 1+ Dungeness crab by tide
height on Transect 1, July 1984 to October 1985 37
21. Average crab densities associated with different intertidal
plant species, all transects combined 37
22. Average crab densities by percent plant cover for the
four most abundant intertidal plant species 39
23. Average crab densities associated with different substrate
materials, both with and without plant cover, all transects
combined 39
24. Average temperatures at low tide for the Lummi Bay inter-
tidal region.................. 41
25. Average salinities at low tide for the Lummi Bay intertidal
region.... 42
26. Size-frequency histograms of Dungeness crab caught in the
beam trawl 45
27. The percent of female Dungeness crab in monthly crab pot
catches in Lummi Bay 47
vi
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LIST OF TABLES
No. Page
1. Average abundances of Dungeness crab per hectare calculated
from beam trawl catches in Lummi Bay from July 1984 to
October 1985 13
2. Average abundances per hectare of Dungeness crab in Lummi
Bay by depth as calculated from beam trawl catches during
1984 and 1985 15
3. Average abundances per hectare of Dungeness crab in Lummi
Bay by transect as calculated from beam trawl catches during
1984 and 1985 15
4. Summary of beam trawl, crab pot and intertidal crab species
composition and Dungeness crab sex, shell condition and
state of reproduction 17
5. Pearson correlation coefficients (r) between beam trawl-
derived Dungeness crab catches (Log,Q transformation) and
catch volumes, substrate materials, trawl depth and speed..... 23
6. Distribution of intertidal sampling effort and catches of
Dungeness crab by plant cover species, all transects and
survey trips combined 38
APPENDIX TABLES
1. Average catches by month of four species of crab in vexar-
lined crab pots set at crab pot Stations 1-4 in Lummi Bay
during 1984 and 1985 58
2
2. Average densities (crabs/m ) of Dungeness crab from
intertidal transect sampling in Lummi Bay from July
1984 to October 1985 61
vii
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ACKNOWLEDGEMENTS
Primary funding for this project was provided by a grant from the
Lummi Indian Tribe. Additional support funds and/or manpower were provided
by a variety of other agencies. Other individuals and agencies supporting
this project were:
Louie Echols, Washington Sea Grant (NOAA)
Ron Westley and Dick Burge, Washington Department of Fisheries
(Shellfish Division)
Bill Obert, Washington Department of Ecology (Shorelands Division)
Catherine Krueger, U.S. Environmental Protection Agency (Office of
Puget Sound)
We thank the following agencies and individuals for their valuable
contributions to this study: Richard Vanderhorst, Paul Hage, Mike McKay,
Merle Jefferson, Dean Mike, Joseph Hillaire, and Tommy Edwards of the Lummi
Indian Tribe; Dick Baumgarner, Randy Butler, Brian Hovis, Walt Cook, Todd
Peterson, and Curtis Dahlgren of the Washington Department of Fisheries;
Chris Dungan, Tony Whiley, Greg Jensen, Jeff Lang, Greg Blair, George
Williams, Ginger Phalen, Sue Cudd and Wayne Palsson of the University of
Washington School of Fisheries.
We extend our sincere appreciation to Frank Proffett and Richard
Shi deler and the residents of the Sandy Point community for their
assistance and permission to use the Sandy Point Marina boat launch ramp.
The helpful coordination and assistance of Steve Babcock and Gail
Arnold of the Seattle District, U.S. Army Corps of Engineers is sincerely
appreciated. Assistance with manuscript preparation was provided by Carl a
Norwood, Judy Carpenter and Carol Sisley. Valuable review comments and
suggestions were provided by Bruce Miller and Tom Wainwright of the School
viii
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of Fisheries; Richard Vanderhorst and Carl Reichhardt of the Lummi Indian
Tribe; and Gail Arnold, Fred Weinmann and Kay McGraw of the U.S. Army Corps
of Engineers.
ix
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FILE COPY
UNIVERSITY OF WASHINGTON
SEATTLE, WASHINGTON 98195
Fisheries Research Institute, WH-10
3 March 1987
Catherine Krueger
U.S. EPA, Office of Puget Sound, M/S 433
1200 Sixth Ave.
Seattle, WA 98101
Dear Catherine:
Please find enclosed five copies of our final report to the Lummi Indian
Tribe titled "Dungeness Crab, Cancer magister, Distribution,
Recruitment, Growth, and Habitat Use in Lummi Bay." This study was
funded, in part, by your office under an EPA/NOAA-Sea Grant Interagency
Agreement IAG No. DW13931825-01-1. Submission of this report represents
partial fulfillment of this agreement.
We very much appreciate your support of our attempts to establish a
long-term data base in Dungeness crab ecology and habitat requirements
in Puget Sound. Only through the cooperative efforts of a variety of
agencies is this type of project possible.
Should you have any questions or require additional copies of the Lummi
Bay report, please call me at 543-7345•
Sincerely,
Paul Dinnel
Principal Research Biologist
PD:cs
Encl.
P.S. Thank you for your kind comments about the Padilla Bay Draft
Report.
2(iO Fisheries Center I 'lele/'/inih: < 20(i I Sj <-Jf-
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INTRODUCTION
The Lummi Indian Tribe has proposed to construct a new public
commercial fishing boat marina complex within a portion of the existing
tribal aquaculture pond in Lummi Bay, Washington. Lummi Bay is situated
adjacent to the Strait of Georgia on the Lummi Indian Reservation in
Whatcom County, approximately 7 nautical miles north of Bellingham,
Washington (Fig. 1). Construction of the marina project in the
aquaculture pond would require dredging a navigation channel approximately
2,200 meters long by 30 m wide across the present intertidal flats, an area
equivalent to about 14 ha and 493,000 cubic meters of dredged materials
(Fig. 2). A major portion of the proposed navigation channel contains
eel grass (Zostera marina and Z. japonica), which has been shown to be
important habitat for many marine animals (Thayer and Phillips 1977),
substrate for Pacific herring (Clupea harengus pallasi) spawn (Palsson
1984) and food for migratory waterfowl (Phillips 1972).
The nearshore area of Lummi Bay supports a commercial and sports
fishery for Dungeness crab (Cancer magister) of which the Lummi tribal
fishermen share in a major portion of the catch. The shallow intertidal
flats of Lummi Bay, especially those areas with eelgrass cover, are
suspected to provide valuable nursery habitat for juvenile Dungeness crab.
Indeed, Dinnel (1971) documented settlement of post-larval (young-of-the-
2
year; 0+) Dungeness crab in eelgrass beds at densities up to 80 crabs/m in
Humboldt Bay, northern California, and Stevens and Armstrong (1984)
reported high densities of 0+ juveniles in and near eelgrass in Grays
Harbor estuary.
In order to satisfy tribal concerns regarding protection of valuable
marine fisheries nursery areas and the environmental impact review process
required by state and federal permitting agencies, the Lummi Indian Tribe
1
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LUMMI
BAY
Belllngham
Everett
VANCOUVER
ISLAND
$3
Port Angeles
Tacoma
Aberdeen
Olympia
WASHINGTON
Nautical Miles
/Seattle
Figure 1. Map of western Washington State showing the location of
Lummi Bay.
Z.
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NEPTUNE
BEACH
LUMMI TIDE
FLATS
SANDY POINT
PROPOSEDV
NA VIGA TIO&
CHANNEL^
v'/ <
MARIETTA
vn
-A
O
-n
tribal.center
•EXISTING
PONO
ROJECT
EXTREME
LUMMI
POINT
GOOSE
BERRY
POINT
BRANT
POINT
-s-
"Z. the
\<\ PORTAGE
I MILE
PORTAGE \ '
Vn\w ISLAND )/
BE LUNG HAM BAY
0 MIGLEYPOINT
n\
O
*31
Gi
POINT FRANCES
Figure 2. Project location map of the proposed Lummi Bay marina
(from COE 1983).
3
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provided funds and assistance to the School of Fisheries of the University
of Washington to conduct a Dungeness crab habitat evaluation study of Lummi
Bay, with special emphasis on the area of the Bay proposed for the new
navigation channel. This study is a portion of a larger study of Dungeness
crab habitat and population dynamics in north Puget Sound initiated in 1984
with funding support from the Washington Sea Grant Program and the
Washington Department of Fisheries (Dinnel et al. 1985).
The specific objectives of the Lummi Bay Crab Habitat Study were as
fol1ows:
1) Estimate Dungeness crab abundances in Lummi Bay with an
emphasis on juvenile crabs.
2) Determine distributions of life history stages by season,
depth and habitat.
3) Determine settlement periods, growth rates and survival
for young-of-the-year crab.
4) Assess potential impacts to Dungeness crab from dredging
of a boat navigation channel through the Lummi Bay tide
flats.
This document is the technical completion report for the Lummi Bay
Crab Habitat Study specific to the marina project and the navigation
channel dredging. Additional information regarding the overall north Puget
Sound Dungeness Crab Study will be available at a later date.
MATERIALS AND METHODS
Sample Methods
Dungeness crab resources and habitat usage in Lummi Bay were
assessed using three different sampling methodologies: 1) trawls made with
a small plumb staff beam trawl; 2) commercial crab pots modified with small
mesh Vexar screen to retain small crabs; and 3) intertidal quadrat sampling
during periods of low tide.
4
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Beam Trawls
Trawling was conducted with a 3 m beam trawl with an effective
fishing width of 2.3 m (Fig. 3). This trawl was designed by Gunderson and
Ellis (1986) for sampling demersal organisms and has been routinely used in
Grays Harbor, Willapa Bay (Armstrong and Gunderson 1985; Gunderson et al.
1985) and North and Central Puget Sound for the last 2 to 3 years.
Intertidal (during high tide) and shallow subtidal (to 12 m depth
below MLLW) trawls were conducted with a 7 m Boston Whaler equipped with a
towing frame and winch. Each subtidal tow was 4 to 5 minutes in duration
while intertidal tows were reduced to 2 to 2.5 minutes due to the large
amounts of algae (especially Ulva) and eel grass (Zostrea marina) caught in
the trawl.
The contents of all trawls were sorted into several categories:
shell, vegetation, rock, wood and debris, crabs (excluding kelp and
decorator crabs, Pugettia sp. and Hyas sp.), and other fish and
invertebrates. Items in each category were weighed and recorded, with the
exception of crabs, which were identified to species, sexed, measured for
carapace width (CW), and checked for molt condition and reproductive stage
of mature females. Temperature and salinity data were collected monthly
from December 1985 to October 1986 from surface and bottom waters at
Stations 7 (intertidal), 8 (-3 m) and 9 (-12 m) (see Fig. 4).
Crab Pots
Commercial-style Dungeness crab pots were generally fished for 24 hr
periods using fresh or frozen fish or clams for bait. Each crab pot,
including the escape rings, was covered with small mesh (approximately 13
mm x 16 mm diamond mesh) Vexar screen to help retain sublegal sized (<159
mm) crab. Retention of crabs less than about 100 mm was incomplete,
however, since small crabs could still exit the slots between the trigger
5
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Figure 3. Diagram of the 3m beam trawl used to assess crab resources in Lummi Bay.
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apparatus in the entrance channels. All crabs caught in the pots (except
kelp or decorator crabs) were processed as noted above for the beam trawls.
Intertidal Quadrat Sampling
Intertidal samples for 0+ and 1+ age crabs were collected along
2
transects by digging 0.25 m samples to a depth of approximately 3 cm.
Each sample was washed in 4-iran mesh nets or screens and sorted in the
field. All crabs were identified, measured as above, sexed if greater than
20 mm carapace width, and returned to the beach. Notes were made of
substrate type, plant cover type and percent (subjective estimates), and
substrate and pool temperatures (at a depth of 1-2 cm) at each sample
location.
Sample Sites
Beam Trawls
Nine beam trawl stations were established in June 1984 along three
transects (Fig. 4), one each in the northern (Stations 1-3), middle
(Stations 7-9), and southern (Stations 4-6) portions of the Bay, and were
stratified by three depths: intertidal (Stations 1,4,7), 3 m below MLLW
(Stations 2,5,8) and 12 m below MLLW (Stations 3,6,9). Four additional
trawl stations were established in the intertidal channels in October 1984
to monitor the channel proposed to be dredged. Trawl Stations 10-12 were
positioned in the "North" Channel (the proposed navigation channel) and
Station 13 established in the "Middle" Channel to act as a "Control"
station. Each station was trawled once per month through October 1985
(except twice during August 1984). Occasional bad weather limited sampling
during a few months.
7
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LUMMI BAY
J = Shallow trawl stations
'•0* ***>*£
(Intertidal)
Figure 4. Locations of the beam trawl stations in Lummi Bay.
8
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Crab Pots
The Vexar-modified crab pots were fished during most months from
October 1984 through September 1985. Two crab pots were fished in the
North Channel (Pot Stations 1 and 2), one pot fished offshore of the North
Channel at a depth of 5 m below MLLW (Pot Station 3) and one pot fished in
the middle "Control" channel (Pot Station 4; Fig. 5).
Intertidal Quadrat Samples
Three intertidal sampling transects were established in Lummi Bay
(Fig. 5). Transect 1 ran parallel to the North Channel beginning at the
foot of the northwest corner of the aquaculture pond dike and extended
westward approximately 2000 m to the extreme low water line (Fig. 5).
Transect 2 ran parallel to the Middle Channel from the foot of the dike
about 1700 m westward to the low water line. Transect 3 in South Bay began
on the upper beach at the foot of Cagey Road and extended westward
approximately 400 m to the low water line. Each transect was generally
sampled monthly although frequency depended on transect and season.
Sampling on each transect was conducted at various intervals (e.g., 0, 100,
300, 500, 700 paces, etc.; 100 paces averaged 84.4^ 1.6 m) out from the
upper beach or dike and samples were selected haphazardly within each
2
habitat type and percentage cover by tossing the 0.25 m sampling quadrat
onto those habitats and digging the material therein. The objective of
this type of stratified sampling (stratified by distance from upper beach,
type of habitat and percent plant cover) was to maximize the information
obtained regarding use of different types of habitats by juvenile crab.
For the stratified sampling program, an attempt was made to balance
sampling effort at each distance on each transect when possible to
facilitate within- and between-transect comparisons of crab densities and
habitat usage (e.g., three samples each of 100%, 75%, 50%, 25% and 0% cover
9
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LU MM I BAY
• * •?
IW'
.'J
4 »
... ... ../.J
POT 11 \ if
POT 2
POT 3
POT 4
«
s •
0 #•
N
T
• •:
• •«
#o/ •
• . :
>-
V\
Caaev Road
\ TRANSECT 3 K
Figure 5. Locations of crab pot stations in the north and middle channels
and the intertidal transects in north, middle and south Lummi Bay.
10
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of the dominant plant(s) at each distance).
Data Analysis
Beam trawl tows varied in the distance the net covered due to the
interaction of many uncontrollable variables, including wind, currents,
motor speed and amount of material caught by the net. Hence, distance
towed was determined by setting floats at the beginning and end of each tow
and measuring the distance between the floats with a calibrated optical
rangefinder accurate to approximately + 10%. The total area swept by the
2
net (m ) was calculated by multiplying the tow distance by the effective
fishing width of the net (2.3 m). Crab catches from each tow were
converted to a standard abundance measurement of estimated crab/hectare
(ha) by the following formula:
2
10,000 m
Estimated crab/ha = (Number of crab caught by net)
area swept
by net
Counts of benthic or epifaunal invertebrates usually show a contagious
(non-random) distribution (Elliott 1977). Hence, all crab catch data were
transformed prior to use in analysis of variance (AN0VA), bivariate
correlation analysis or other similar statistical analyses by the following
formula:
Xt = Log (Abundance + 1)
10
where Xt is the transformed variable (Elliott 1977).
Crab pot catches are reported as raw catches since it is impossible to
calculate an "area fished" by a baited pot and the catches per unit time
are probably not linear due to a variety of factors (i.e., number of crabs
already in the pot, age of the bait, day vs. night, escapement of small
crabs back out entrance channel "triggers", etc.)
11
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2
Intertidal crab densities are reported as crabs/m by multiplying the
2
catches/0.25 m by a factor of 4.
RESULTS
Beam Trawls
Abundances of Oungeness crab (number/hectare) calculated from the
monthly beam trawls in Lumrni Bay are summarized in Table 1 and presented
graphically in Figure 6. The average overall trawl abundance of Dungeness
crab in Lummi Bay was 320 ^24 (+1 standard error) with a monthly high of
969 + 414 (Sept. 1985) and a monthly low of 1 + 1 (Feb. 1985) (Table 1,
Fig. 6). Abundances of Dungeness crab were consistently higher during the
summer-fall (July to Oct.) period of 1985 as compared to the same time
period of 1984 for all stations combined (Fig. 6). Dungeness crab were
very scarce in the beam trawl samples during winter at average abundances
of only 1 to 15 crab/ha from January to March 1985.
Relative to depth, Dungeness crab catches were almost always highest
along the subtidal "dropoff" contour at -3 m followed by intertidal,
channel and, lastly, the -12 m contour (Fig. 6, Table 2). Geographically,
there were no obvious differences in the calculated abundances of Dungeness
crab between the North (Stations 1-3), Middle (Stations 7-9) and South
(Stations 4-6) transects (Table 3; see Fig. 4 for station locations).
Seven species of demersal crabs (excluding kelp and decorator crabs)
were caught in the trawls and of the total, Dungeness crab equalled 71.2%
of the crab catch (Table 4). Of the Dungeness crab caught in the beam
trawls, approximately 31% were males, 39% females and 30% of unknown sex
(i.e., juveniles <20 mm CW) (Table 4). For shell condition, approximately
69% of the Dungeness crab had hard to very hard (i.e., yellow shells, often
with encrusting barnacles) shells while the other 31% had recently molted
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Table 1. Average abundances of Dungeness crab per hectare calculated
from beam trawl catches in Lummi Bay from July 1984 to
October 1985.
Average Abundance Standard
Cruise # Date n Per Hectare Error
2
July 18-21, 1984
8
483
187
3
Aug 3-6
9
217
89
5
Aug 16-18
9
246
76
7
Oct 20-22
12
180
67
8
Nov 17-18
13
78
40
10
Dec 19
12
38
19
11
Jan 25-27, 1985
12
7
3
12
Feb 15-17
11
1
1
13
March 15-17
13
15
8
15
April 17-20
13
138
73
16
May 15-18
13
167
80
17
June 12-16
13
572
168
18
July 9-12
13
797
491
19
Aug 6-10
13
350
160
20
Sept 5-10
12
969
414
22
Oct 16
5
860
698
All
Cruises Combined
11.3
320
24
13
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1000
750
All Stations Combined — Beam Trawls
«
lo
«
o
«
z
w>
•
CL
Xi
(B
(S
OB
0
e
«
OB
500
250
X = 320 ± 24
i^i.
i
111 1 ' *^***' ¦1 t i - * i I i '
JASONDJ F
1984
A M J
198S
J A S O
1250
Intertidal
(0
c
®
a
9
O)
(B
k.
9
>
<
500
250
0
1250
1000
750
500
250
0
I 1000 x = 235 ± 99
Q
- 750
o
>»
V
J—J ¦ T—
•I7f4 Channel
X =160 ± 57
>3 Meter
2560
2301 3652
X =642 ± 166
U
\
\
1 1 1, ' -
¦
¦12 Meter
X =79 ± 22
i ..I
J ASONDJ FMAMJ JASO JASONDJ FMAMJ JASO
1984 1985 1984 1985
Figure 6. Average estimated abundances (+ 1 standard error) of Dungeness crab
calculated from beam trawl catches in Lummi Bay from July 1984 to
October 1985 (see Fig. 4 for station locations).
14
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Table 2. Average abundances per hectare of Dungeness crab in Lummi Bay
by depth as calculated from beam trawl catches during 1984 and 1985.
Depth
(meters below MLLW)
n
Average Abundance
Per Hectare
Standard
Error
0 (Intertidal)
46
235
99
1 (Channels)
43
160
57
3
45
642
166
12
42
79
22
All
176
320
24
Table 3. Average abundances per hectare of Dungeness crab in Lummi Bay by
transect as calculated from beam trawl catches during 1984 and 1985.
Location
n
Average Abundance
Per Hectare
Standard
Error
North Transect
(Stations 1-3)
44
269
67
Middle Transect
(Stations 7-9)
45
390
160
South Transect
(Stations 4-6)
42
320
116
Channel Stations
(10-13)
43
160
57
15
-------
and possessed soft or very soft shells (Table 4). Soft-shelled crabs were
seasonal with the majority occurring from June through August in both 1984
and 1985. The majority of very hard shelled crabs (especially females)
were found from April to July, prior to the summer molting and soft shell
period. Very few gravid female Dungeness crab (only 2.4% of all females)
were caught in the beam trawls (Table 4), and almost all were captured in
March, April and May of 1985.
Average Dungeness crab size varied by season as well as by trawl depth
with an overall average carapace width (CW) of 66 + 46 mm (+1 standard
deviation) for all samples (Fig. 7). The generally small average size of
crabs caught during the summer months reflects the influx of young-of-the
year (YOY) and the increased catchability of the 1+ year class at shallow
stations. The large average crab sizes during the winter months reflects
the capture of very few individuals, most being mature crab (Figs. 7 and
8).
Histograms of monthly Dungeness crab carapace width frequencies
(Fig. 8) show that YOY crabs settled from approximately June through
September 1984 with carapace widths of 5-15 mm. Relatively little growth
took place prior to or during winter. The first substantial growth of the
1984 year class was not evident until about May 1985 and thereafter crabs
reached an average CW of 70-80 nun by October 1985 as 1+ juveniles. The
1983 year class (1+ in 1984) was very evident in the April and May 1985
samples with carapace widths in the range of 100 to 130 mm. The abundances
of these 2 year old crabs then decreased through June and July and dropped
to almost zero after August 1985, suggesting a movement offshore to areas
deeper than -12 m.
16
-------
Table 4. Summary of beam trawl, crab pot and intertidal crab species
composition and Dungeness crab sex, shell condition and state of
reproduction.
Percentage of Catch
Characteristic
Beam trawls
Crab pota Intertidal
Crab species;
C. magister
C. productus
C. gracilia
C. oregonensis
Telmessus
Hemigrapsus
Lophopanopeus
Total count
Dungeness Crab Sex:
Male
Female
Unknown (Juveniles <20.0 mm)
Total Count
71.2$
10.7
8.1
6.0
2.4
0.9
0.7
3,121
31 .0
38.9
30.1
2,221
93.4$
5.6
0.2
0
0.8
0
0
882
51.7
48.2
0.1
824
89.8
2.2
0.8
0
2.2
4.9
_0
716
5.1
4.2
90.7.
643
Dungeness Crab Shell Condition (for crabs >100 mm):
Very soft
Soft
Hard
Very hard
1.3
29.3
65-0
4.4
Total Count 839
State of Reproduction (Dungeness Females):
Not gravid
Gravid
97.6
2.4
0.4
4.5
66.1
29.0
493
100
0
NA1
NA
Total Count
246
226
1NA = Not applicable since all but one Dungeness crab from the intertidal
samples were juveniles <100 mm carapace width.
17
-------
E
E
160
120
80
40
All Stations Combined - Beam Trawls
X =66 t 46
UJ
O
<
a.
<
s
<
o
UJ
o
<
UJ
>
1984
160
120
80
40
0
160
120
80
40
0
Intertidal
X = 33 t 26
Channe
-3 Meter
/
X = 44 f 30 A
X = 68 t 45 •
I I I I I I I I
-12 Meter
_ X = 105 t 45 e
_ A = 1UO T 45 • \ , •
:-W V\/ '
1 * 1 I 1 1 1
l i l i
JASONDJ FMAMJJAS
1984 1985
JASONDJFMAMJ JAS
1984 1985
Figure 7. Average carapace widths (+ 1 standard deviation) of Dungeness crab
caught by beam trawl in Lummi Bay from July 1984 to September 1985.
18
-------
JULY 64
(n* 193)
DEC 84
20 40
loo 1
140 IGO 180 200
JULY 85
(n=467)
UulfMt|wh>
k
AUG 85
(n-310)
SEPT 85
(n-467)
Iff"
iiiiiiyiiiiLihi
IW 1» 140 160 lib lot
Carapace Width ( mm)
Figure 8. Size-frequency histograms of Dungeness crab caught in the
beam trawl for each sample month, all stations combined.
-------
The data presented above indicate that there was a gradual shift to
deeper water as Dungeness crabs grew. Indeed, histograms (Fig. 9) of
trawl-caught crab widths by depth substantiate this trend.
In June 1985, all 1+ crab (1984 year class) were caught intertidally
or in the shallow channels cutting across the intertidal flats while 100%
of 2+ crab (1983 year class) were caught at the -3 in stations. Older crab
(1982 and older year classes) ranged between the -3 m and -12 m stations,
probably moving to deeper waters by the following September.
As described above, the composition of Dungeness crab in the beam
trawl catches was a function of both season and depth. Other factors which
may affect the distribution (or catch) of Dungeness crab are substrate
composition and/or epibenthic materials (which may provide cover or forage
for fish, crab, and invertebrates), and speed of the trawl. The
relationship of each of these factors to Dungeness crab abundances was
analyzed by bivariate correlation analysis (SPSS Regression; Nie et al.
1975). The most signifcant Pearson correlation coefficient (r) was with
trawl speed where r = -0.2251 (significance (p) = 0.001; Table 5)
indicating a negative correlation between tow speed and crab catches. One
reason for this negative correlation could be that the fastest tow speeds
may not have allowed enough time for crabs buried in the substrate to
emerge and be caught by the net. The slowest average speeds were at the
intertidal, -3 m and -12 m stations where crab catches were usually the
highest (Fig. 10, top). There was no significant correlation between trawl
depth and Dungeness crab catches. However, as shown above, there was an
obvious relationship between trawl depth and Dungeness crab age group.
There was no significant correlation between crab catches and total
catch volume of substrate materials (Table 5), but there were significant
correlations with several of the substrate components. There was a
20
-------
10
8
6
4
2
0
10
8
6
4
2
0
10
8
6
4
2
0
10
8
S
4
2
0
JJ
INTERTIDAL TRAWL
(n=298)
20 40 60 80 100 120 140 160 180 200
itili
MJjJ.
-3m TRAWL
(n=1641)
llllllillllllMlfalUtu
20 40 60
100 120 140 160 180 200
li
-12 ib TRAWL
(n=697)
.,U,lJJLDJil.UlU.il
20 40 60 80 100 120 140 160 180 200
1 llu
CHANNEL TRAWL
(n=265)
A..L.MA...U
20 40 60 80 100 120 140 160 180
Carapace Width (mm)
200
ure 9. Size-frequency histograms of Dungeness crab caught
in the beam trawls in four areas of Lummi Bay
(stratified by depth), all sample months combined.
21
-------
significant positive correlation of r = 0.1402 (p = 0.03, Table 5) with
plant material (various algae, kelps, and eelgrass) while a significant
negative correlation existed for rock (r = -0.1741, p = 0.01). Abundant
plant material provides cover for juvenile crab (common in summer catches)
in intertidal areas, and detrital algae and eelgrass were commonly caught
at the -3 m stations where crab catches were highest on the average (642
crab/ha; Fig. 10, bottom; Fig. 7). Catches of rock (gravel and small
cobble) had a significant negative correlation due (in part) to the fact
that most rock was caught at Station 6 (a -12 m station) where Dungeness
crab were rarely caught (Fig. 10, bottom). Indeed, Station 6 appeared to
provide optimum habitat for red rock crab (C. productus) and purple crab
(C. gracilis) in contrast to all other trawl stations in Lummi Bay which
favored Dungeness crab.
Air and water temperatures and salinities at the trawl stations varied
seasonally as would be expected. Water temperatures were lowest in
December 1984 at about 5° to 6°C and highest in July 1985 at 16° to 18°C
(Fig. 11). Intertidal water temperatures were almost always isothermal due
to the shallow water depths (0 to 3 m) and high degree of wind and tidal-
induced mixing. Bottom temperatures were slightly different at the -3 m
and -12 m stations where warmest temperatures reached 16° and 13°C,
respectively during the summer months. Salinities varied from lows of
about 23 °/oo in July 1985 to highs of 33 °/oo in January 1985 (Fig. 12).
Intertidally, there was a 1 to 2 o/oo difference in surface and bottom
salinities during the winter when the near shore area was subjected to
increased freshwater runoff, but essentially isohaline during the rest of
the year. At the -3 m and -12 m stations, salinities were usually within
1 °/oo of each other for the bottom and surface waters with no consistent
-------
Table 5. Pearson correlation coefficients (r) between
beam-trawl derived Dungeness crab catches
(Log^ transformation) and catch volumes,
substrate materials, trawl depth and speed.
Factor r Significance of r
Catch volume
0.1069
0.07
Plant material
0.1402
0.03
Animal (fish and inverts)
-0.0865
0.12
Rock
-0.1741
0.01
Shell
-0.0995
0.09
Wood and debris
-0.0590
0.21
Trawl depth
-0.0922
0.10
Trawl speed
-0.2251
0.001
23
-------
80
« 60
Iti
g s
Wz
5S
<
o
40
20
D
70
60
50
?*«
¦v. fn
3 (AS
i -9 9>
3 Hi &
w ffl w
©
1 4 7 10 11 12 13 2 5 8 3 6 9
INTERTIDAL CHANNEL -3 METER "12 METER
STATION
Plant Animal Shell Wood Rock
TH
INTERTIDAL CHANNEL "3 METER
DEPTH
-12 METER
Figure 10. Top: Average beam trawl tow speed and volume of substrate
material caught in the trawl at each Lummi Bay trawl station.
Bottom: Breakdown by category of substrate materials caught
in the beam trawl for each set of stations stratified by depth.
24
-------
pattern to the differences between them (Fig. 12). The one exception was
during June of 1985 when a plume of low salinity (down to 23 %o) water was
detected (probably from the Fraser River in British Columbia).
Crab Pots
A total of 882 crabs were caught in crab pots set at the four sampling
stations (see Fig. 5 for locations) in Lummi Bay from August 1984 to
Sept. 1985 (Appendix Table 1). Dungeness crab accounted for 93.4% of the
catch with the remainder being C. productus (5.6%), C. gracilis (0.2%) and
Telmessus (0.8%) (Table 4). The Dungeness crab male/female ratio in the
crab pot catches was essentially 1/1, 95% had shell conditions of hard or
very hard and no gravid females were caught (Table 4). Only 5% of the
Dungeness crab in the pots were soft or very soft vs. 31% in the beam
trawls. This difference suggests that soft crabs were less active or more
reclusive than hard crabs. The absence of gravid females in the pots is
probably also indicative of a reclusive behavior during egg incubation or
aggregation of females in other locations.
The seasonal catch of crabs in pots followed the general pattern of
the beam trawls with highest numbers caught during summer and fall (June-
Nov.) and least caught during winter (Dec.-March) (Fig. 13). The highest
average crab catches (17.8 4.5/pot) were from Station 1, that closest to
the dike in the North Channel, although there were no statistically
significant (t-test; p = 0.05) differences in catches between any of the
North Channel stations (1-3) versus the Middle Channel station (4) (Fig.
13). The Middle Channel (control) station was closest in average catch to
the North Channel Station 2, with 10.4 + 3.1 vs. 12.3 + 2.3 crabs/pot,
respectively.
The average carapace width of all Dungeness crab caught in the crab
pots was 108 _+ 31 ran, with monthly averages ranging from a high of 127 mm
25
-------
20
-
15
. AIR
10
-
5
«
0
- /
•
-5
D J
4
/
—^ I
' 1
1985
20
15
10
Surface
QSL
5
0
WATER
Bottom
• Intertidal
/ \
1 * ¦
<
CC 20
O-
LlJ
-3m
1 '
i ) I
12 m
.'•v
15
10
5
0
20
15
10
5
0
Figure 11. Air and water temperatures from trawl stations 7 (intertidal),
8 (-3 m) and 9 (- 12 m) in Lummi Bay from December, 1984 to
October, 1985.
J J >1 L
1985
26
-------
35
30 - •*
25
201 i I
SURFACE
,•
BOTTOM
Intertidal
j 1 ¦
¦ »
O
O
35
30
— 25
<
CO
20
J L
J I I I
3 m
35 r
30
25
20
/ \
~
•* - ®
8^-— 9
J L
J I L
12 m
J L
Figure 12.
DJ FMAMJ J A S 0
1985
Surface and bottom water salinities from trawl stations 7 (intertidal),
8 (-3 m) and 9 (-12 m) in Lutnmi Bay from December 1984 to October
1985.
27
-------
to a low of 74 nsn (Fig. 14). This is in contrast to sizes of Dungeness
crab caught by beam trawl which averaged between 33 to 44 mm CW. Rarely did
Dungeness crab <50 mm in size enter the pots (or if they did enter, they
were able to escape back out the crab pot entrance channel triggers). Most
crabs caught in the pots were in the age groups 1+ to 2+ with few distinct
patterns evident by month (Fig. 15). One distinct pattern that was evident
was the influx of large crabs in the 120 to 150 mm size range during April
and May. Approximately 90% of these crab were large, non-gravid females
which then disappeared in June to be replaced almost exclusively by 2 year
old crabs averaging about 70 to 80 mm (Fig. 15).
For the North Channel stations (1-3), there was an increase in the
average size of Dungeness crab with distance away from (westward) the
aquaculture pond dike (Fig. 16). There was no significant difference (t-
test; p = 0.05) in average crab sizes between any of the North Channel
stations versus the Middle Channel (control) station. However, the average
size of Dungeness crab at the Middle Channel station was closest in
agreement to North Channel Station 2 with average sizes of 112 +_ 26 and 119
+ 27 mm, respectively.
Intertidal Quadrat Sampling
A total of 21 intertidal survey trips were conducted between July
1984 and October 1986. All three transects were not surveyed on each trip
due to constraints of manpower and time. Surveys of Transect 3 were
discontinued after June of 1985.
Five species of crab were caught in the intertidal quadrat samples of
which 89.8% were Dungeness crab (in contrast to 93.4% in pots and 71.2% for
the beam trawls; Table 4). Only 9.3% of the Dungeness crab sampled from
the intertidal quadrats were large enough to be sexed (i.e., >20 mm CW) of
28
-------
All Stations Combined — Crab Pots
o
tL
° •
w 0.
t S
E «
m "
I %
« C
A ®
® a
<
c
3
a
X = 13.7 ±1.1
/
\
A S O N
1984
A S
Station 1
X= 17.8 * 4.5
e
a- 20
Station 3
X=12.5 + 1.2
a 30
o>
CO
5 20
>
<
10
\/
/
i i >
» t
¦
ASONDJ FMAMJ JAS
1984 1985
Station 2
X=12.3 t 2.3
I t
/
•V
v
/
¦
Station 4
X=10.4 t 3.1
¦ . .
ASONDJ FMAMJ J AS
1984 1985
Figure
13. Average catches (± 1 standard error) of Dungeness crab in crab pots set
at four stations in Lummi Bay from August 1984 to September 1985
(see Fig. 5 for station locations)
29
-------
E
E
160
120
80
40
All Stations Combined - Crab Pota
x =108 ±31
<
160
120
80
40
0
160
120
80
Station 1
Station 2
X = 87 + 27
V /\
\
•
v.—
X=119t27
Station 3
' 1 1 1 ' 1 1 LJ.
Station 4
. X = 124 + 25
w
\
0 ' 1 1 ' * ' ' 1 1 1 ' ¦
ONDJ FM AM J JAS
1984 1985
/V
• •
X =112 ±26
/ x_
ONDJFMAMJ JAS
1984 1985
Figure 14. Average carapace widths (+ 1 standard deviation) of Dungeness
crab caught in crab pots in Luirani Bay from October 1984 to
September 1985.
30
-------
12t
9->
6-.
3--
OCTOBER 84
(n-95)
12r
9-
6-.
3--
APRIL 85
(n-103)
12j
9--
6-.
3--
0-»
I"1
-U
NOVEMBER 84
(na156)
12T
9--
6-.
3--
IIIIIMIIfllllllll|l|lll
HAY 05
(n»121)
I
12
9
6
3'
0
mrnmpmnip
DECEMBER 84
(n«8)
»piiMiii|in
12t
9'
6+
3
0
JUNE 85
(n=40)
12
9
6
3
0
JANUARY 85
(n=28)
npnn
12-r
9--
6-
3--
0-n
JULY 85
(n=73)
PU.1M,
12-,
9-
6-
3-
0-
FEBRUARY 85
(n-17)
12y
9--
S--
3-
0--
AUGUST 85
(n=65)
Oil*.
!2j
9-.
6-.
3-.
0
M
II
MARCH 85
(n»69)
0 20 40 60 80 100 120 140 160 180 200
12
9'
6
3'
0
SEPTEMBER
(na107)
jl
Lj1l111i.il,,,
20 40 60 80 100 120 140 160 180 200
Carapace Width (mm)
Figure 15. Size-frequency histograms of Dungeness crab caught
in the Vexar-modified crab pots by sample month,
all stations combined.
31
-------
which the sex distribution was essentially even (Table 4). No gravid
females were caught in the intertidal samples and only 1 of 643 Dungeness
crab caught in the intertidal samples was >100 mm.
Intertidal abundances of Dungeness crab in Lummi Bay showed a seasonal
cycle similar to that determined for both the beam trawls and the crab pots
(Appendix Table 2). A rapid increase in crab density occurred through the
months of July and August, and peaked in mid-August of both 1984 and 1985
(Fig. 17). These increases coincided with the periods of settlement and
were, in fact, due to the abundances of newly metamorphosed first and second
instar crabs. Following the period of highest settlement in August 1984,
a general decline in density was observed, falling from a peak average of
2 2
8.8 crab/m to less than 1/m in June 1985.
During 1984, megalopae were observed in the intertidal samples from
the first Lummi Bay sampling effort (July 12) until September 21. In 1985,
the first megalopae appeared on July 1; however, none were observed after
August 28, suggesting a shorter period of settlement for this year.
The occurrence of first instars coincided with that of the megalopae
for both years and underscores the longer period of settlement observed in
1984 than in 1985. The 1985 settlement appeared greater in magnitude than
2
1984 with a high average density of 18.2 crab/m in 1985 compared to 8.8
2
crab/m for 1984 (Fig. 18). However, by October 1985, the average density
2 2
had fallen to nearly the same value as for October 1984 (2.7/m and 2.1/m ,
respectively).
Growth of 0+ crabs continued from the time of settlement until
October, after which time little growth was seen until the following May.
During this period of arrested growth (October through early April),
substrate and water temperatures had fallen below 10°C. The 1984 year class
resumed growth in about April 1985 (Fig. 19).
-------
io T
8
6"
4-
2-
oi
POT STATION #1
(n»283)
inmli
10
8-
6"
4-
2"
oL
20 40 60 80 100 120 140 160 180 200
POT STATION #2
(n-212)
rUJr
10
8-
6-
4 •
2--
oL
20 40 60 80 100 120 140 160 180 200
POT STATION #3
(n®268)
jJl iJljJlL itmll
UvrulV
10
8 -
6 •
4 ¦¦
I-
0
I 111 II V VIII V
20 40 60 80 100 120 140 160 180 200
POT STATION U
(n-105)
JJU
rtlMtrtul
20 40 60 80 100 120 140 160 180 200
Carapace Width (mm)
Figure 16. Size-frequency histograms of Dungeness crab caught
in the Vexar-modified carb pots set at each pot
station in Lummi Bay, all sample months combined
(see Fig. 5 for station locations).
33
-------
The virtual disappearance of the previous year class from the June
1985 intertidal samples coincided with their appearance at the channel and
subtidal beam trawl stations (Fig. 8). The emmigration of this year class
from the intertidal flats into the channels closely preceded recruitment of
the 1985 year class (Fig. 19).
The annual pattern of crab abundance and timing of arrival and
movement was similar on all three transects (Fig. 18 and Appendix Table 2).
Statistical comparisons (t-test) of average crab densities and carapace
widths (calculated using only survey trips on which both Transects 1 and 2
were sampled) showed no significant (p = 0.05) differences between the two
transects for either parameter.
On Transect 1 the vertical (and consequently, horizontal) distribution
of 0+ and 1+ crab followed a trend of increasing abundance with decreasing
elevation in the intertidal zone. The lowest average density, 1.3
2
crab/m , occurred between +1.0 and +2.0 feet above MLLW while the highest,
2
4.3 crab/m , occurred between -1.0 and -2.0 feet below MLLW (Fig. 20).
Densities above the MLLW mark were roughly half of those below this level.
Within Lummi Bay, 98.5% of the juvenile crabs sampled in the
intertidal zone were associated with some form of plant cover. Crab
densities varied according to the plant species, ranging from a low of 2.1
2
crab/m for mixed Zostera (i.e., a mixture of Z. marina and Z. japonica) to
2
5.7/m for 111va (Fig. 21 and Table 6). An AN0VA performed on the average
crab densities grouped by plant species showed no significant (p = 0.05)
difference between them. When all plant categories were grouped, there was
significantly (p = 0.05) greater density compared to samples with no plant
cover. The percent cover provided by the different plant species was
generally positively correlated to crab density (Fig. 22), a trend best
-------
AH Transacts Combinad — Intartidal Surveys
Figure 17. Average (± 1 standard error) densities of juvenile
Dungeness crab from July 1984 to October 1985, all
intertidal transects combined.
INTERTIDAL CRAB DENSITY
By Transect
20 —i—i—i—i—i—i—i—i—i—i—i—i—i—i—r
15
10
a
L
(_>
0
— Transect 1
— Transect 2
•••• Transect 3
JASON.DJFMAMJJASO
1984 1985
Figure 18. Average densities of juvenile Dungeness crab for
intertidal transects 1, 2 and 3, July 1984 to
October 1985 (see Fig. 5 for transect locations)
35
-------
30
20
10
0
12 JULY 84 40
Cn-32> 3Q ¦
20
JO
of MlllilUi
21 SEPT 84 40
(n-87) 30
20
10
0
4 MARCH B5 40
(""4) 30
20
10
I1 '"I I 0
29 JULY 85
(n-39)
J_JL
26 JULY 84 40
(n-81)
or nrr QJ m
10 APRIL 85 40
(n-39) 30
16 AUG 85
(n-82)
"L
» "4'"' ....I.I,!
40t
30
20
10
0
9 AUG 84 40
(n-14) ju
20
10
- 0
25 NOV 84 40
(n-29) ^
20
10
¦ 1„F 0
JUL
I *
6 MAY 85 <0
(n-37) j,,
20
10
_ 0
28 AUG 85
(n-83)
llMfcHf.i
-Vwnmpmwpimmj*
jjlu.
-*r-4-
24 AUG 84 40
(n=64) a
20
10
0
"1 r I
I >¦"
9 JAN 85 40t
(n-4> a
20
10
0
"T" I
1 ,lint I,
5 JUNE 85 40
(n-12) jo
20
10
0
23 SEPT 85
(n-19)
40t
30
20
10
»
6 SEPT 84 40T
a
20
10
0
1 JULY 85 40
(n-31) 3Q
20
J » jJ
tilth ,U Jn, ,IHH,I I, „—,—, 0 flfll UL„I 1 nig,
10 20 3D 40 50 GO 70 80 90 100 "¦ ® ® ® 60 70 80
15 OCT 85
(n-15)
90 100
Carapace Width ( mm )
Figure 19. Size-frequency histograms of Dungeness crab caught in the intertidal
quadrat samples along three transects in Lummi Bay, all transects
and stations combined by month.
-------
Abova
2.0 ft
2.0
1.0
ELEVATION
(in ft. O.O
from MLLW)
-1.0
Figure 20.
-2.0
Balos
-2.0 ft
BEACH ELEVATION
VS.
INTERTIOAL CRAB DENSITY
0
85
340
715
1055
1435
2025
~ISTANCE (m)
(From dika)
0 12 3 4
DENSITY
(Crabs/™2)
Average densities of 0+ and 1+ Dungeness crab by
elevation on Transect 1, July 1984 to October 1985,
DENSITY
(Crabs/m1)
PLANT COVER SPECIES
vs*
INTERTIOAL CRAB DENSITY
Ulva sp. Mixed Zostora Entaro- Mixad Zostara Hixad No Plant
Alga narina aorpha Zostara jap. Zostara Cover
& Alga
COVER SPECIES
Figure 21. Average crab densities associated with different Lntertidal
plant species, all transects combined.
37
-------
Table 6. Distribution of intertidal sampling effort and catches of Dungeness crab by plant
cover species, all transects and survey trips combined.
Average
Plant cover species crab density Sampling Effort Crab Distribution
(Crab/m ) Number of Percentage Number of Percentage
samples of samples crab of crab
Zostera marina
3.9
347
36.6$
336
50.1%
Zostera japonica
2.4
123
13.0
75
11.3
Ulva sp.
5-7
38
4.0
54
8.1
Enteromorpha sp.
3.4
14
1.5
12
1.8
Mixed Zostera
2.1
15
1.6
8
1.2
Mixed Algae
4.0
9
0.9
9
1 .4
Mixed Zostera & Algae
3.3
191
20.1
159
24.0
No plant cover
0.2
207
21 .8
10
1.5
Other
0
5
0.5
0
0
TOTALS
949
100.0
663
100.0
-------
DENSITY 3"
(Crabs/a ) 4..
PERCENT PLANT COVER
vs«
INTERTIDAL CRAB DENSITY
japanicfl
1-20Z 21-402 41-60X
PERCENT COVER
61-80Z
81-100*
Figure 22. Average crab densities by percent plant cover for the four
most abundant intertidal plant species. Averages are plotted
for each 20% interval, all transects combined.
4-.
DENSITY
(Crabs/m )
Z-.
1-.
O-l-
SUBSTRATE MATERIAL
VS.
INTERTIDAL CRAB DENSITY
Sand
Plant Cover
Present
(n®741)
Plant Cover
Absent
(n»208)
Cobbla
/Said
Shall
/Sand
Graval
/Sand
Silt
SUBSTRATE MATERIAL
Figure 23. Average crab densities associated with different substrate
materials, both with and without plant cover, all transects
comb ined.
39
-------
demonstrated for U1va.
Average crab densities associated with substrate materials were quite
different depending upon whether plant cover was present or not (Fig. 23).
Crab densities were lower in the absence of plant cover, but the relatively
uniform nature of the substrate within Lummi Bay made it difficult to
discern any well defined preference for substrate materials in the absence
of plant cover.
Temperatures were recorded for air, substrate, and water in standing
pools and adjacent channels (Fig. 24). Little variation was observed
between the different transects* however, seasonal fluctuations were high
(e.g., average substrate temperatures ranged between a low of 0.1°C in
February to a high of 22.2°C in August 1985). Salinity is shown for pools
and channels within the intertidal region in Figure 25. The lower channel
salinities presumably represent freshwater input from the Lummi River and
other terrestrial sources.
DISCUSSION
It is evident from the data presented above that the population
characteristics of Dungeness crab in Lummi Bay are complex and dynamic and
that Lummi Bay provides important habitat for most of the post-larval life
history stages of this species. General patterns of Dungeness crab
distribution, seasonality, recruitment, survival, and growth have emerged
from this study. Some of the most important findings can be summarized as
follows:
1) Dungeness crab was the dominant crab species (excluding kelp crabs) in
Lummi Bay and comprised 78% of all crabs sampled followed by Cancer
productus (8%), gracilis (6%) and Telmessus (3%).
40
-------
30
m «
•
25
•
•
•
AIR
-¦
20
•
•
¦
•
IS
•
¦
•
10
•
-j
5
•
•
•
-¦
0
r
-¦
w
30
. •
25
r
SUBSTRATE
20
m
15
•
~
10
5
J
0
-f
-5
III'
WATER
— Pools
Channel
Figure 24. Average temperatures at low tide for the Lummi Bay intertidal
region.
41
-------
35 x
30--
INTERTIDAL SALINITY
SALINITY
(ppt)
25-
20-
POOLS
CHANNEL
is-
Fob
~H 1—
Apr May
1985
Jun
Jul
Aug
Figure 25. Average salinities at low tide for the Lummi Bay intertidal
region.
42
-------
2) Each of the three sampling methods catches crabs differently in regard
to size class selectivity, catch efficiency and degree of
quantification possible. The intertidal quadrat sampling was
virtually 100% efficient, easy to quantify, but was limited to
intertidal areas frequented by crab <1 year old. Beam trawls were
possible in all areas, could be quantified reasonably well, but varied
in capture efficiency from less than 1% for young-of-the-year (YOY) in
eel grass (Dinnel et al. 1985) or gravid females solidly buried in the
substrate (Armstrong et al. 1987a) to almost 100% during the summer
when crabs are active in sandy areas devoid of cover (Dinnel et al.,
in progress). Pots can be fished in areas difficult to trawl but
do not catch small crab (<50 mm) and such data provide only relative
measures of crab abundance.
3) Regardless of the sample method, a seasonality in crab abundance
was evident with the highest catches during the summer months and
the lowest during the winter. Intertidally, this pattern of seasonal
abundance was due to the summer settlement of many post-larval crabs
with few of these new recruits surviving until winter. Subtidally,
the apparent low winter crab populations may be due to poor gear
efficiency because of the relatively inactive and reclusive (i.e.,
buried in the substrate) nature of this species during the cold winter
months.
4) Settlement of 0+ crab begins in about July of each year and continues
until September. Mortality of the new recruits is high during this
time, probably due to predation by a variety of fish, birds and
invertebrates (including cannabalism). The YOY are highly associated
with any type of cover where survival may be highest because of
reduced predation.
43
-------
5) One of the most interesting findings of this study is that Dungeness
crab age group distribution is dependent on depth and that older
animals often aggregate by sex. Generally, successful recruitment of
0+ crabs occurred in intertidal and shallow subtidal vegetated areas.
The 0+ remain in the shallow areas for the first year, averaging only
about 15-20 mm CW in the first winter. Growth resumes during the
summer of the second year when they reach an average size of about
80 ran and move into channels and shallow subtidal areas along the
intertidal "dropoff." During the summer of their third year, these
crabs average about 100-130 mm in size and move out of the shallow
water areas of Lummi Bay where they may form aggregations by sex
as noted in several other areas of Puget Sound (Dinnel et al., in
progress; Dinnel et al. 1986a). Larger crabs in their fourth year (or
older) may then move back to shallow water where the males enter the
pot fishery and the females may aggregate during the egg incubation
period.
The stratification and movement of crabs by age group is outlined in
detail by the size-frequency histograms in Figure 26. This figure
shows a cycle of Dungeness crab abundances at four strata (intertidal,
shallow channel, the -3 m "dropoff" area, and -12 m depth offshore) in
Lummi Bay from July 1984 to October 1985. The arrows show that the
1984 year class moves out of the intertidal into the shallow channels
in about June and thence into the "dropoff" (-3 m contour) area by
July where they grow quickly to an average size of about 80 mm by
October. At about the same time, the 1983 year class was found to
move away from the -3 m "dropoff" area out to the -12 m offshore area
(and probably beyond) so that intermixing of the year classes is
44
-------
>
o
c
In*) 5)
JUN 05
STRATA 2
(n*126)
JUN 65
STRATA 1
(n*22)
JUN 35
STRATA 3
(n-98)
jun as
STRATA 4
k
jul as
STRATA 2
(n«6)
JUL 95
JUL 85
STRATA 3
ln»344)
\ JUL 85
. STRATA 4
\ (n-28)
STRATA 1
AUG 85
STRATA 2
Cn-20)
AUC 85
STRATA 3
(n-i92)
SEP 85
STRATA 2
(r>-38)
SEP 85
STRATA 1
Cn*61)
se? es
STRATA 3
irf>67>
I
OCT 85
OCT 85
STRATA 2
(n-IO)
OCT 35
j'RATa 3
(n«96)
OCT 95
STRATA 4
(n«ll)
STRATA
1
li a «o o « ids >20 >60 itt ao
ia & 40 ito ifr ito iio ax
1 2c
-------
minimized. Following the synchronized outward movements of the 1984
and 1985 year classes, the 1985 YOY metamorphose from megalopae and
establish residency in their favored strata, the intertidal/shallow
subtidal eel grass zone where they grow to about 20 mm by November,
essentially "hibernate" during the winter and begin the cycle anew in
1986.
6) The sex ratio of crabs caught in the crab pots fluctuated seasonally,
exhibiting a greater number of males from July through October.
During March, April and May, females dominated the catches (Fig. 27).
This was attributable to mature, non-ovigerous females, >100 mm
carapace width, which appeared first in March catches at the deepest
station (3) and not until April and May at the channel stations. It
appears that following egg hatching these females become active and
begin foraging, making them susceptible to capture by pots. Their
appearance first at the deeper station (3) and subsequently at the
shallower channel stations (1, 2, & 4), suggests a preference (while
ovigerous) for greater depths than what is available in the channels.
Potential Impacts of the Proposed Navigation Channel
The primary objective of this study was to define potential effects on
Dungeness crab of dredging a navigation channel through the Lummi Bay tidal
flats. The potential effects can be divided into short term and long term
effects.
Short Term Effects
Short term effects can be defined as the crab entrained and killed by
initial dredging of the navigation channel. Dredging of the navigation
channel would impact about 14.2 ha and remove 493,000 cubic meters of
material. Of this 14.2 ha, approximately 3.6 ha of eel grass beds would be
removed, the remaining acreage being unvegetated shallow channel areas (COE
-------
100
90
80
70
60
PERCENT so
40
30
20
10
0
PERCENT OF FEMALES
IN CRAB POT CATCHES
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
1984 1985
Figure 27. The percent of female Dungeness crab in monthly crab pot catches
for Lumrai Bay (Pot Stations 1 through 4 combined). Note the
dominance of females in the March, April and May 1985 catches.
47
-------
1983; Lummi Indian Fisheries 1984). Dredging is currently planned using a
hydraulic dredge (with confined pipeline disposal) during the winter
(December-March) to minimize impacts to other species (e.g., juvenile
salmon and herring spawning). How, then, do these potential dredge-related
impacts translate into crab mortality given the 1984-85 crab data presented
above?
In the intertidal portion of the proposed navigation channel,
2
Dungeness crab densities averaged about 1 crab/m during the December to
March period (intertidal quadrat samples; Fig. 18). During this same time,
almost no crab were caught by beam trawl in the same area (Fig. 6).
However, we suspect that the beam trawl efficiency was greatly reduced
during this period due to inactivity and burial by the crabs in the
substrate. Our rationale for this is based on our diver transect
observations in other areas where crabs were uncovered during winter
surveys by disturbing the bottom by hand which resulted in uncovering of
buried lethargic crabs (Armstrong et al. 1987a). Hence, for purposes of
this discussion, we will use the average overall beam trawl-derived crab
density for the channels (160 crab/ha; Fig. 6) and the average winter
2
densities (1.0 crab/m ) found in the winter of 1984 intertidal surveys
(Fig. 18).
Using the preceeding assumptions, the number of crab in the proposed
dredge area can be calculated as follows:
2
1) [3.6 ha eel grass] [crab density of 1/m ] =
36,000 crab (primarily 0+)
2) [10.6 ha of shallow channel] [160 crab/ha] =
1,696 crab (primarily 1+ or older)
48
-------
The total estimated number of crab in the proposed dredge area (based
on winter 1984-85 surveys would be 36,000 + 1,696 = 37,696. These
calculations show that by far the greatest number that could be affected is
YOY crabs living in the eel grass beds.
The calculations become less certain from this point on. The best
crab entrainment/mortality data to date has been generated from studies in
coastal estuaries such as Grays Harbor (Tegelberg and Arthur 1977; Stevens
1981; Armstrong et al. 1982), systems that are substantially different than
the eel grass flats of Lummi Bay. In Grays Harbor, Stevens (1981) and
Armstrong et al. (1982) found that crab entrainment rates generally ranged
from 0.13 to 0.65 crabs/cubic meters of material dredged by a pipeline
suction dredge operating with a conventional cutterhead. Unfortunately, no
estimates were given in these studies as to how many crab were actually
present in the dredged area. Indeed, if we use the lowest value of 0.13
crabs/cubic meter and apply this value to the Lummi Bay Navigation
Channel, we would calculate that 64,090 crab would be entrained - more than
estimated to be present in the winter of 1984/85 based on the above
calculations. From another dredge entrainment study in Grays Harbor,
Dinnel et al. (1986b) estimated that a hopper dredge, operating with a
draghead rather than a cutterhead, entrained only 15.9% of the Dungeness
crab present in the area based on side-by-side beam trawl studies.
However, this information is also of limited use because of differences in
size of crab (average CW = 88 mm) and habitat (deeper channels, no
vegetation) in that study compared to Lummi Bay. Hence, we are left with
two methods of calculating what may happen in Lummi Bay. A "least impact"
best case scenario indicates that 15.9% (or 5,994 crabs; based on Dinnel et
al. 1986b) of the crabs present could be entrained and killed (assuming
-------
pipeline disposal behind a dike would kill 100%). A "worst impact"
scenario suggests that essentially all of the estimated 37,696 crabs would
be entrained and subsequently killed. There are two main reasons why a
worst impact scenario might be realized:
1) Most of the crabs potentially affected in Lummi Bay will be young
crab (0+ or 1+ age classes) which typically survive by hiding rather
than fleeing to escape as older crab usually do. This "hiding reflex"
will be characteristic of small crab in the area of the proposed
channel where vegetation is present.
2) Temperatures during the proposed winter dredge period will be very low
(typically 6-8°C). Low temperatures reduce activity in crabs and seem
to induce a "semi-hibernation" mode which would make it very difficult
for them to move away from a dredge suction head. This "hibernation"
mode was quite evident during winter intertidal sampling. Small crabs
dug from the substrate were quite torpid and moved only slightly
compared to crabs dug out during warmer temperatures.
The calculations presented above are based on the density of crabs
observed with the best, but potentially inefficient, sampling gear for
buried crabs and only during the winter of 1984-85. Presently, we do not
know how much interannual variability in recruitment, density and survival
of Dungeness crab occurs in Lummi Bay or, in general, for the inland waters
of Washington. Thus, these abundance estimates should be reassessed for
the year when dredging takes place.
It was estimated above that somewhere between 5,994 and 37,696 crabs
may be killed by the dredging activity proposed for Lummi Bay (assuming
crab abundances similar to 1984 during the year of dredging). Most of
these crabs would be of the 0+ and 1+ age groups, of which only a fraction
would naturally survive to enter the fishery (or reproductive effort for
-------
the females). While natural mortality rates are poorly quantified for most
age classes of Dungeness crab, two values do appear in the literature. Jow
(1965) estimated a natural annual mortality rate of 0.15 based on tag
returns. Gotshall (1978), also working with tag returns, estimated a
natural annual mortality range of 0.005 to 0.183.
These rates, however, are not satisfactory for application to the
present study since both Jow and Gotshall tagged only adult crabs (i.e.,
crabs >100 mm carapace width). Current work by Armstrong et al. (1987b),
using several years of data from Grays Harbor, Washington, suggests that
natural mortality of late 0+ and 1+ age crabs may be as high as 84% to 90%.
Hence, the application of any natural mortality factor to the foregoing
Lummi Bay crab impact analysis should proceed with caution and the
understanding that a high degree of uncertainty is involved, especially
since juvenile crab habitats-in Puget Sound are substantially different
from Grays Harbor.
One additional aspect of the life cycle which is poorly known makes
short-term impacts difficult to predict. Very few gravid females were
caught during this study. However, diving surveys used in conjunction with
trawl surveys in a similar area of North Puget Sound have shown that high
densities of gravid females can be present along the "dropoff" at depths of
-2 to -6 m below MLLW (the subtidal eelgrass zone; Armstrong et al. 1987a).
In this case the beam trawl was an ineffective tool for catching these
females since they remained solidly bruied in the substrate, even when
lightly disturbed. Presently, the distribution of mature females in and
around Lummi Bay is unknown. A large number of mature females were found
in the crab pots in the spring of 1985 and again in April 1986 beam trawls
(Dinnel et al., in progress). This pattern suggests that the gravid
-------
females do utilize the nearshore area of Lummi Bay during the winter but
are not caught in the sampling gear until they shed their eggs and begin
moving around in the spring. Diver surveys are recommended for future
assessment for gravid females.
Long Term Effects
Long term effects on crab populations are considered those caused by
long term loss (or gain) of preferred or necessary habitats. COE (1983)
predicts the loss of 3.6 ha of eelgrass habitat during initial dredging.
However, eelgrass would be replanted over a portion of this area.
Additionally, strong arguments have been presented (Hage 1984a, b) that
stabilization of the North Channel by dredging would eliminate channel
meandering which erodes portions of the adjacent eelgrass flats. Thus, the
combination of mitigation as eelgrass transplants together with cessation
of lateral erosion may increase the amount of eelgrass habitat present in
Lummi Bay.
Regardless of gain or loss of eelgrass habitat, preliminary estimates
can be generated for future crab losses (or gains) based on the 1984-85
crab data. Initial settlement of 0+ in 1984 and 1985 was as high as 8.8
2
and 18.2 crab/m , respectively. As noted above, these densities then
2
declined to approximately 1 crab/m during the winter and remained stable
at this level until spring (recent sampling in 1986 suggests roughly the
same pattern of settlement and survival). The issue of paramount
importance regarding the value of eelgrass habitat in Lummi Bay is "how
many crab does this habitat produce that eventually recruit to the
commercial/sport fishery" (and how many females survive to reproductive
age). Clearly, this value cannot be determined by the magnitude of initial
settlement since most of the first or second instars do not survive. The
value, then, might be determined by assessing the density of crab surviving
52
-------
to a size at which they are ready to migrate to a more suitable habitat.
For 0+ Dungeness crab in Lummi Bay, migration appears to occur in June
following the year of settlement as is evident by the disappearance of
these young crabs from the intertidal samples (Fig. 18) and the increase of
this age class in the May and June beam trawls (Fig. 8). Hence, the first
good measure of a given year class success might be obtained by intertidal
quadrat surveys during the first set of good daytime low tides (typically
in April) before movement off the flats takes place.
Using this idea as a guide, the average density of the 1984 year class
2
in April 1985 was about 1 crab/m (same density as noted above for the
December-March period since mortality was essentially zero during the
winter; Fig. 18). We can gauge the value of eelgrass beds for this year
2
class as equal to approximately 1 crab/m . Hence, the permanent loss (or
gain) of 1 ha of eelgrass could be equivalent to the loss (or gain) of
approximately 10,000 crab in each succeeding year (interannual variability
in recruitment success or survival will change this estimate). Predicting
crab recruitment to the fishery (or gravid females) is again another very
uncertain step since no good measure is available for natural mortality
rates for any age class of crabs in Puget Sound.
A second interactive aspect of the dredging modification of the North
Channel concerns the change in depth of what is now a very shallow channel
to a depth of about -4 m below MLLW. Evidence from the beam trawl sampling
suggests that dredging may substantially improve the habitat for 1+ and 2+
age classes of crab. Figure 6 shows an average estimated abundance of crab
in the shallow channels of 160 crab/ha while trawls at the -3 m depth
contour produced crab catches equal to an average abundance of 642 crab/ha,
a substantial increase over the shallow channels. Consequently, dredging
-------
of the aquaculture pond for the moorage basin (-3 to -4 m depth) should
also improve this area for crabs.
RECOMMENDATIONS
Recommendations for future studies are divided below between general
(those designed to understand the basic ecology of Dungeness crab and the
fishery) and project-specific (those designed to monitor actual impacts of
the proposed project).
General Recommendations
Almost two years of field data have been collected on Dungeness crab
in Lummi Bay. Because of this, and because of the importance of crab
resources in this area, we highly recommend continuation of long-term
monitoring to refine the type of information presented above, determine
ranges in year-to-year variability in the population dynamics of the
various year classes, and further determine the importance of nearshore
tidelands to recruitment of this valuable species. Specifically, we
recommend:
1) Continuation of intertidal quadrat sampling for monitoring recruitment
densities, survival and growth of future year classes. This should be
done by establishing a permanent test plot (e.g., 100 m x 100 m in the
area of the North Channel) and sampling randomly during the summer for
estimates of settlement strength. This same plot should be sampled to
determine overwintering survival once or twice in early spring (April)
before the 0+ crabs move into channels.
2) Trawling should be continued during spring and summer at stations
specifically selected to produce the best information on 1+ and 2+ age
classes of crabs. This information, together with the intertidal
data, can then be compared to subsequent commercial catches in Lummi
-------
Bay to shed light on several important questions: e.g., is year class
success controlled by density dependent factors and if so, at what
age?; how important is Lummi Bay as a nursery area?; do juveniles
raised in Lummi Bay return to the Lummi Bay fishery?, etc.
3) Three and four year old crabs apparently spend some time in deeper
waters. These areas should be located, and the related habitat values
for Dungeness crab described.
4) The location of gravid Dungeness crab females in or around Lummi Bay
should be determined by diving surveys.
Project-Speci fic Recommendati ons
Specific recommendations for monitoring the impacts of channel
dredging include:
1) Determine densities of crab present intertidally and in the channel
subtidally prior to dredging.
2) Monitor the dredge spoils plume (assuming a pipeline disposal system)
for crabs.
3) Quantify crab use of revegetated areas and of the newly dredged
channel (and moorage basin) using the data presented in this report as
a baseline and also comparing with the undredged middle (control)
channel.
4) Determine presence or absence of gravid females in the outer
navigation channel area prior to dredging.
55
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LITERATURE CITED
Armstrong, D.A., B.G. Stevens and J.C. Hoeman. 1982. Distribution and
abundance of Dungeness crab and Crangon shrimp, and dredging-related
mortality of invertebrates and fish in Grays Harbor, Washington.
Tech. Rpt. to Washington Department Fisheries and U.S. Army Corps
of Engineers by School of Fisheries, Univ. of Washington, Seattle.
349 pp.
Armstrong, D.A., and D.R. Gunderson. 1985. The role of estuaries in
Dungeness crab early life history: A case study in Grays Harbor,
Washington. Pp. 145-170 Ln: Proceedings of the Symposium on Dungeness
Crab Biology and Management. University of Alaska, Alaska Sea Grant
Rpt. No. 85-3.
Armstrong, D.A., J.L. Armstrong and P.A. Dinnel. 1987a. Ecology and
population dynamics of Dungeness crab, Cancer magister, in Ship
Harbor, Anacortes, Washington. Final Rpt. to Leeward Development
Company and Washington Department Fisheries by School of Fisheries,
Univ. Wash., Seattle, Wa. FRI-UW-8702. 79 pp.
Armstrong, D.A., T. Wainwright, J. Orensanz, P. Dinnel and B. Dumbauld.
1987b. Model of dredging impact on Dungeness crab in Grays Harbor,
Washington. Final Rpt. to Battelle Northwest Laboratories, Sequim,
Wash, and U.S. Army Corps of Engineers, Seattle, WA. FRI-UW-8701.
COE (U.S. Army Corps of Engineers). 1983. Lummi Bay Marina, Whatcom
County, Washington: Draft detailed project report and draft
environmental impact statement. U.S. Army Corps of Engineers,
Seattle, Wa. 51 + pp.
Dinnel, P.A. 1971. Recruitment, distribution, mortality, and growth of the
1970 and 1971 year classes of the gaper clam, Tresus capax (Gould,
1850) (Bivalvia: Mactridae), in Humboldt Bay, California. M.A. Thesis,
Humboldt State College, Areata, Ca. 63 pp.
Dinnel, P.A., D.A. Armstrong and C. Dungan. 1985. Initiation of a Dungeness
crab, Cancer magister, habitat study in North Puget Sound. Pp. 327-
337 _In: Proceedings of the Symposium on Dungeness Crab Biology and
Management. University of Alaska, Alaska Sea Grant Rpt. No. 85-3.
Dinnel, P., D. Armstrong, B. Miller and R. Donnelly. 1986a. U.S. Navy
homeport disposal site investigations: winter, spring, summer and
fall cruise reports for U.S. Army Corps of Engineers by School of
Fisheries, Univ. Wash., Seattle.
Dinnel, P.A., D.A. Armstrong and B.R. Dumbauld. 1986b. Impact of dredging
and dredged material disposal on Dungeness crab, Cancer magister, in
Grays Harbor, Washington during October, 1985. Final Rpt. to U.S.
Army Corps of Engineers, Seattle District, by School of Fisheries,
Univ. Wash., Seattle. FRI-UW-8611. 30 pp.
56
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Dinnel, P.A., D.A. Armstrong and R.O. McMillan. In progress. North Puget
Sound Dungeness crab studies.
Elliott, J.M. 1977. Some methods for the statistical analysis of samples
of benthic invertebrates. Scientific Publ. 25, Freshwater Biol.
Assn., Ferry House, Ambleside, England. 160 pp.
Gunderson, D.R. and I.E. Ellis. 1986. Development of a plumb staff beam
trawl for sampling demersal fauna. Fisheries Research, 4:35-41.
Gunderson, D.R., D.A. Armstrong, and C. Rogers. 1985. Sampling design and
methodology for juvenile Dungeness crab surveys. Pp. 135-144 In:
Proceedings of the Symposium on Dungeness Crab Biology and Management.
University of Alaska, Alaska Sea Grant Rpt. No. 85-3.
Gotshall, D. 1978. Catch-per-unit-of-effort of northern California
Dungeness crabs, Cancer magister. Calif. Fish Game, 64(3):189-199.
Hage, P. 1984a. Letter dated 19 July 1984, to G.I. James, Fisheries
Director, Lurnini Indian Tribe.
Hage, P. 1984b. Letter dated 26 September 1984, to G. Arnold, R. Trumble,
R. Burge and D. Stout regarding Lummi Bay Marina.
Jow, T. 1965. California-Oregon cooperative crab tagging study. Pac.
Marine Fish. Comm. Rpt. Vol. 16-17:51-52.
Lummi Indian Fisheries. 1984. Survey of Zostrea marina L. in the proposed
access channel, Lummi Bay Marina. Lummi Indian Tribal Fisheries
Rpt., Bellingham, Wa.
Nie, N.H., C.H. Hull, J.G. Jenkins, K. Steinbrenner and D.H. Bent. 1975.
Statistical Package for the Social Sciences (SPSS), Second Edition.
McGraw-Hill Book Co., New York. 675 pp.
Palsson, W.A. 1984. Egg mortality upon natural and artificial substrata
within the Washington State spawning grounds of Pacific herring (Clupea
harengus pallasi). M.S. Thesis, School of Fisheries, Univ.
Washington, Seattle.
Phillips, R.C. 1972. Ecological life history of Zostera marina L.
(eelgrass) in Puget Sound, Washington. Ph.D. dissertation, Univ.
Wash., Seattle. 154 pp.
Stevens, B.G. 1981. Dredging-related mortality of Dungeness crabs
associated with four dredges operating in Grays Harbor, Washington.
Final Rpt. by Washington Department Fisheries for U.S« Army Corps of
Engineers, Seattle District. 148 pp.
Tegelberg, H. and R. Arthur. 1977. Appendix N: Distribution of Dungeness
crabs (Cancer magister) in Grays Harbor, and some effects of channel
maintenance dredging. U.S. Army Corps of Engineers, Seattle District.
Thayer, G.W. and R.C. Phillips. 1977. Importance of eelgrass beds in Puget
Sound. Mar. Fish. Review Paper 1271: 18-22.
57
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APPENDIX TABLES
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Appendix Table 1. Average catches by month of four species of
crab in Vexar-lined crab pots set at crabpot
stations 1-4 in Lummi Bay during 1984 and
1985.
Average Average Number of Crabs
Sample Hours
Month/Year Size(n) Fished C_. magister C.. productus qraci 1 is Telmessus
Station #1 = Inner North Channel:
Oct., 1984
2
23.5
8.0
0
0
0
Nov.
2
22.5
37.0
0
0
0
Dec.
1
68.0
2.0
0
0
0
Jan., 1985
2
23.0
5.5
0
0
0
Feb.
1
29.0 '
5.0
0
0
0
March
1
24.0
9.0
0
0
0
April
1
22.0
25.0
0
0
0
May
2
24.5
10.0
0
0
1.0
June
1
24.0
39.0
0
0
1.0
July
1
24.0
8.0
0
0
2.0
Aug.
1
4.0
22.0
0
0
0
Sept.
1
22.0
53.0
0
0
0
Station #2 =
Outer
North Channel:
Oct., 1984
2
23.5
12.0
1.0
0
0
Nov.
2
22.5
23.5
0
0
0
Dec.
1
68.0
3.0
0
0
0
Jan., 1985
2
23.0
1.0
0
0
0
Feb.
1
29.0
6.0
0
0
0
58
-------
Aflfirearcdiix Table 1. Average catches by month of four species of
crab in Vexar-lined pots set at crabpot
((Gjxrntt*1 d-) stations 1-4 in Lummi Bay during 1984 and
1985.
AverageAverage Number of Crabs
Sample Hours
Mteth/Year Size(n) Fished C. magister C^. productus C. gracilis Telmessus
Station #2 = Outer North Channel:
M&rch
1
24.0
3.0
0
0
0
April
1
22.0
14.0
2.0
0
0
May
2
24.5
17.5
0.5
0
0
July
2
23.0
11.0
3.5
0
0
Aug.
1
4.0
20.0
3.0
0
0
Sept.
1
22.0
21.0
1.0
0
0
Static
m 3 = Offshore
of North Channel
(~5m Depth)
Aug.,
1984 27
12.4
17.3
3.3
0.1
0
Sept.
9
9.8
15.1
0.8
0.1
0
Oct.
5
14.8
8.6
0.8
0.2
0
Nov.
2
22.5
16.5
3.0
0
0
Dec.
1
68.0
1.0
1.0
0
0
J'fflET. ,
1985 2
23.0
4.0
0
0
0
Feb;.
1
29.0
4.0
0
0
0
March
5
16.8
10.2
0.8
0
0
April
1
22.0
21.0
0
1.0
0
Way
2
24.5
7.0
10.5
0
0
July
2
23.0
16.0
1.0
0
0
Sept.
1
22.0
6.0
1.0
0
0
59
-------
Appendix Table 1. Average catches by month of four species of
crab in Vexar-lined pots set at crabpot
(Cont'd ) stations 1-4 in Lummi Bay during 1984 and
Average Average Number of Crabs
Sample Hours
Month/Year Size(n) Fished C_. magister C. productus C_. graci 1 is Telmessus
Station 4 = Middle Channel:
Dec., 1984
1
68.0
1.0
0
0
0
Jan., 1985
2
23.0
3.5
0
0
0
Feb.
1
29.0
2.0
0
0
0
March
1
24.0
3.0
0
0
0
April
1
22.0
25.0
1.0
0
0
May
2
24.5
10.5
0
0
0
Aug.
1
4.0
20.0
0
0
0
Sept.
1
22.0
25.0
0
0
0
60
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Appendix Table 2 . Average densities (crabs/m^) of Dungeness crab from
intertidal transect sampling in Lummi Bay from July
1984 to October 1985.
Transect Number
Sample Dates
1
2
3
July 12-14, 1984
5.8
1.0
July 27-30
5.7
7.4
3.1
Aug. 9-12
8.8
Aug. 24-27
6.3
1.6
6.1
Sept. 6
1.5
Sept. 21-24
3.2
2.7
5.8
Oct. 25-29
2.1
0.7
4.8
Nov. 23-28
0.5
1.3
1.7
Dec. 19-20
1.1
Feb. 3-6, 1985
0.6
March 4-5
0.0
April 7-10
1.7
1.3
1 .2
May 6-9
2.3
1.3
June 2-6
0.6
0.0 .
June 21-22
0.0
June 30-July 3
0.4
2.3
July 28-Aug. 1
1.7
3.1
Aug. 14-17
18.2
Aug. 26-28
9.3
5.7"
Sept. 22
4.4
Oct. 15
2.7
3.4
61
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