Biological Report 82(11.121) 

December 1989 

Species Profiles: Life Histories and 

Environmental Requirements of Coastal Fishes 

and Invertebrates (Pacific Southwest) 

DUNGENESS CRAB 

Fish and Wildlife Service 

Coastal Ecology Group 

Waterways Experiment Station 

U.S. Department of the Interior U.S. Army Corps of Engineers 
Biological Report 82 (11.121) 

TR EL-82-4 

December 1989 

Species Profiles: Life Histories and Environmental Requirements 

of Coastal Fishes and Invertebrates (Pacific Southwest) 

DUNGENESS CRAB 

Gilbert B. Pauley, David A. Armstrong, Robert Van Citter, and G. L. Thomas 

School of Fisheries and Washington Cooperative Fishery Research Unit 

University of Washington 

Seattle, WA 98195 

Project Officer 

David Moran 

U.S. Fish and Wildlife Service 

National Wetlands Research Center 

1010 Gause Boulevard 

Slidell, LA 70458 

Performed for 

Coastal Ecology Group 

Waterways Experiment Station 

U.S. Army Corps of Engineers 

Vicksburg, MS 39180 

and 

U.S. Department of the Interior 

Fish and Wildlife Service 

Research and Development 

National Wetlands Research Center 

Washington, DC 20240 
This series may be referenced as follows: 

U.S. Fish and Wildlife Service. 1983-19-. Species profiles: life histories and environmental requirements of coastal fishes and invertebrates. U.S. Fish Wildl. Sew. Biol. Rep. 82(11). U.S. Army 

Corps of Engineers, TR EL-82-4. 

This profile may be cited as follows: 

Pauley, G.B., D.k Armstrong, R. Van Citter, and G.L. Thomas. 1989. Species profiles: life histories 

and environmental requirements of coastal fishes and invertebrates (Pacific Southwest)--Dungeness 

crab. U.S. Fish Wildl. Sew. Biol. Rep. 82(11.121). U.S. Army Corps of Engineers, TR EL-82-4. 

20 PP- 
PREFACE 

This species profile is one of a series on coastal aquatic organisms, principally fish, of sport, commercial, 

or ecological importance. The profiles are designed to provide coastal managers, engineers, and biologists 

with a brief comprehensive sketch of the biological characteristics and environmental requirements of the 

species and to describe how populations of the species may be expected to react to environmental changes 

caused by coastal development. Each profile has sections on taxonomy, life history, ecological role, 

environmental requirements, and economic importance, if applicable. A three-ring binder is used for this 

series so that new profiles can be added as they are prepared. This project is jointly planned and financed by 

the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service. 

Suggestions or questions regarding this report should be directed to one of the following addresses. 

Information Transfer Specialist 

U.S. Fish and Wildlife Service 

National Wetlands Research Center 

NASA-Slidell Computer Complex 

1010 Gause Boulevard 

Slidell, LA 70458 

U.S. Army Engineer Waterways Experiment Station 

Attention: WESER-C 

Post Office Box 631 

Vicksburg, MS 39180 
CONVERSION TABLE 

Metric to U.S. Customary 

Multiply BY 

millimeters (mm) 0.03937 

centimeters (cm) 0.3937 

meters (m) 3.28 1 

meters 0.5468 

kilometers (km) 0.6214 

kilometers 0.5396 

2 

square meters (m ) 10.76 

square kilometers (km2) 0.3861 

hectares (ha) 2.471 

liters (1) 0.2642 

cubic meters (m3) 35.3 1 

cubic meters 0.0008 110 

milligrams (mg) 0.00003527 

grams (g) 0.03527 

kilograms (kg) 2.205 

metric tons (t) 2205.0 

metric tons 1.102 

kilocalories (kcal) 3.968 

Celsius degrees (O C) 1.8 (" C) + 32 

U.S. Customary to Metric 

inches 25.40 

inches 2.54 

feet (ft) 0.3048 

fathoms 1.829 

statute miles (mi) 1.609 

nautical miles (nmi) 1.852 

square feet (ft2) 0.0929 

square miles (mi2) 2.590 

acres 0.4047 

gallons (gal)3 3.785 

cubic feet (ft ) 0.0283 1 

acre- feet 1233.0 

ounces (02) 28350.0 

ounces 28.35 

pounds (lb) 0.4536 

pounds 0.00045 

short tons (ton) 0.9072 

British thermal units (Btu) 0.2520 

Fahrenheit degrees (" F) 0.5556 (" F - 32) 

To Obtain 

inches 

inches 

feet 

fathoms 

statute miles 

nautical miles 

square feet 

square miles 

acres 

gallons 

cubic feet 

acre-feet 

ounces 

ounces 

pounds 

pounds 

short tons 

British thermal units 

Fahrenheit degrees 

millimeters 

centimeters 

meters 

meters 

kilometers 

kilometers 

square meters 

square kilometers 

hectares 

liters 

cubic meters 

cubic meters 

milligrams 

grams 

kilograms 

metric tons 

metric tons 

kilocalories 

Celsius degrees 
CONTENTS 

Page 

... PREFACE ....................................................... 111 

CONVERSION TABLE ............................................. iv 

FIGURES ....................................................... vi 

ACKNOWLEDGMENTS ............................................ vii 

NOMENCLATURE/TAXONOMY/RANGE ............................... 1 

MORPHOLOGY/IDENTIFICATION AIDS ............................... 1 

REASON FOR INCLUSION IN SERIES ................................. 3 

LIFEHISTORY ................................................... 4 

Mating ....................................................... 4 

Eggs and Fecundity ................................................ 4 

Larvae ....................................................... 5 

Juveniles ....................................................... 7 

Adults ....................................................... 8 

GROWTH CHARACERISTICS ....................................... 8 

THEFISHERY ................................................... 9 

Commercial Fishery ............................................... 9 

SportFishery .................................................... 12 

ECOLOGICAL ROLE .............................................. 12 

ENVIRONMENTAL REQUIREMENTS ................................. 12 

Temperature .................................................... 12 

Salinity ....................................................... 13 

Temperature-Salinity Interactions ...................................... 13 

Substrate ....................................................... 14 

REFERENCES ................................................... 15 
FIGURES 

pa@ 

Dungeness crab ........................................ 1 

Distribution of the Dungeness crab in California ................. 2 

Abdominal differences between female and male Dungeness crabs ..... 3 

Life cycle stages of the Dungeness crab ....................... 6 

Mean carapace width of male and female crabs from central California. 

1977-1980 ............................................ 9 

Dungeness crab landings by season for Pacific Coast states and 

the Province of British Columbia ............................ 10 

Dungeness crab landings for central and northern California ......... 11 

Egg-brooding periods of the Dungeness crab at various laboratory 

seawater temperatures .................................... 13 
ACKNOWLEDGMENTS 

We thank Vali Frank for her assistance with the graphics. We gratefully acknowledge the review 

of this manuscript by Paul Dinell, Fisheries Research Institute, University of Washington, Seattle, 

and David Somerton of the National Marine Fisheries Service. Partial support for David Armstrong 

to acquire and analyze some of the original data to produce this report was provided by Washington 

Sea Grant. 
Figure 1. Dungeness crab. 

NOMENCLATURE/TAXONOMY/RANGE 1921; Butler 1956; Butler 1%1; Stevens 

1982). The distribution of the Dungeness 

Scientific name ....... Cancer magister Dana crab in the Pacific Northwest and the ports 

Preferred common name ... Dungeness crab of major commercial landings are shown in 

(Figure 1) Figure 2. 

Other common names ........ Pacific edible 

crab, edible crab, market crab, commercial 

crab MORPHOLOGY/IDENTIFICATION AIDS 

Class ...................... Crustacea 

Order ...................... Decapoda 

Infraorder ................... Brachyura 

Family. .................... Cancridae 

Geographic range: Coastal waters along the 

west coast of North America from Unalaska 

Island in the north to Mexico in the south 

(Schmitt 1921; MacKay 1943; Butler l%la; 

Mayer 1973). The species ranges from the 

intertidal zone to a depth of at least 180 m 

and inhabits substrates of mud, mud with 

eelgrass (Zostera sp.), and sand (Schmitt 

Dorsal and ventral anatomy of Cancer crabs 

were illustrated by Warner (1977). The following morphology and identification aids were 

taken from Rudy and Rudy (1979). Size (type 

specimen): carapace 120.7 mm long x 177.8 mm 

wide. Color: beige to light brown with blue 

trim and hue, darkest anteriorly, often light 

orange below, sometimes light gray-purple 

below; inner sides of anterior feet and hands 

crimson, fingers not dark. Eyes: eyestalks short, 

orbits small. Antennae: antennules folded 

lengthwise: antenna1 flagella short, more or less 

hairy. Carapace: broadly oval, uneven but not 
Figure 2. Distribution of the Dungeness crab in California. 
highly sculptured; granular; widest at 10th 

tooth, no rostrum. Frontal area: narrow with 

five unequal teeth, not markedly produced 

beyond outer orbital angles; middle tooth 

largest, more advanced than outer pair; outer 

pair form inner angles of orbit. Teeth: (anterolateral) 10, counting orbital tooth; widest at 

10th tooth, which is large and projecting; all 

teeth pointed, with anterior separations. 

Posterolateral margins: unbroken, entire, without 

teeth, meet antero-lateral margins with distinct 

angle. Abdomen: narrow in male, broad in 

female (Figure 3). Chelipeds: fingers not dark; 

dactyl spinous on upper surface; fied finger 

much deflexed; hand with six carineae on upper 

outer surface; wrist (carpus) with strong inner 

spine. Walking legs: rough above; broad and 

flat (especially propodus and dactylus of last 

pair). Juveniles: antero-lateral and posterolateral margins meet at a distinct angle; 

carapace widest at 10th tooth; postero-lateral 

margin entire; carpus of cheliped with single 

spine above, fingers light colored; carapace not 

as broad as adults. 

The red rock crab, Cancerproductus, also has 

10 antero-lateral teeth; frontal teeth are 

unequal. However, this species differs from C. 

magister in that the frontal area is markedly 

pronounced beyond outer orbital angles, 

cheliped fingers are black, and the carapace is 

widest at eighth antero-lateral tooth. It attains 

a width of 7 inches. 

The rock crab, Cancer antennarius, like C. 

productus, is dark red with black-tipped 

chelae, is widest at the eighth tooth, but is redspotted on its ventral surface. It attains a width 

of about 13 cm. Cancer oregonensis (Oregon 

Cancer crab) is a small, oval crab with 12 

antero-lateral teeth. Both the slender crab 

(Cancer gracilis) and Cancer jordani, two rather 

uncommon species, have nine antero-lateral 

teeth; C. gracilis rarely exceeds a width of 8 cm. 

The yellow crab, Cancer anthonyi, which is 

found south of Humboldt Bay, has large smooth 

claws with black tips, is yellowish-brown with a 

wash of purple anteriorly, has 9 antero-lateral 

spines and attains a width of 15 cm. Identification keys to the genus Cancer were prepared 

by Kozloff (1974) and Carlton and Kuris (1975). 

REASON FOR INCLUSION IN SERIES 

The Dungeness crab supports a valuable 

commercial and sport fishery along the west 

Figure 3. Abdominal differences between female (left) and male (right) Dungeness crabs. Only males, 

which possess a slender abdomen, may be kept by sport and commercial crabbers. 
coast of the United States. It occupies 

ecological niches in both marine and estuarine 

waters and is ecologically important as both 

predator and prey at all life stages. Recent 

studies on the environmental consequences of 

dredging in estuaries have established a strong 

probability that the Dungeness crab population 

will be seriously reduced by habitat alteration 

from dredging unless proper precautions are 

taken to reduce losses (Armstrong et al. 1982; 

Stevens and Armstrong 1984). The loss of vital 

estuarine habitat could significantly reduce 

recruitment to the offshore fishery (Armstrong 

and Gunderson 1985). 

LIFE HISTORY 

Mating 

Dungeness crabs mate from April to 

September in British Columbia (MacKay 1942; 

Butler 1956), mostly in March and April (D.k 

Armstrong, unpubl. data) but sometimes in May 

and June in Washington (Cleaver 1949); and 

March to July in California (Poole and Gotshall 

1965). Mating occurs in nearshore coastal 

locations in the west coastal region of the 

Pacific Northwest. Premolt female crabs are 

located by adult males for mating, possibly 

through a pheromonal homing system similar to 

those used by other crab species (Knudsen 

1964; Edwards 1%6; Hartnoll 1969). The 

female is held by the male in a premating 

embrace up to 7 days prior to her molting 

(Snow and Neilsen 1966). Approximately 1 h 

after molting of the female is completed, the 

hardshell male and softshell female mate. The 

male gonopods are inserted into the 

spermathecae of the female and spermatophores 

are deposited. Following copulation, the female 

may be embraced again by the male for a 

period of up to 2 days. Both premating and 

postmating embraces may serve to protect the 

female from predation, while insuring the 

mating success of the male by guarding the 

female against other males (Snow and Neilsen 

1966). The male spermatophores in the 

spermathecae contain sperm that may be viable 

for many months (MacKay 1942), often through 

molting until a second egg extrusion (Orcutt 

1978). 

Ew and Feamdiy 

Actively molting female crabs are more 

fecund than non-molting crabs, even though 

they may be the same size (Hankin et al. 1985). 

Eggs are not fertilized until extrusion, at which 

time they are attached to the female pleopod 

setae and are carried beneath the abdominal 

flap (MacKay 1942; Stevens 1982; Wild 1983); 

they hatch in 60 to 120 days. Eggs are 

extruded from September to February in British 

Columbia (MacKay 1942; Butler 1956), from 

October to December in Washington (Cleaver 

1949; Mayer 1973), from October to March in 

Oregon (Waldrom 1958), and from September 

to November in California (Orcutt et al. 1976; 

Wild 1983). An egg mass may contain from 

one to two million eggs (Wild 1983), and a 

female may produce up to five million eggs in 

three or four broods during her lifetime 

(MacKay 1942). Eggs are orange at extrusion, 

becoming progressively darker in color as they 

develop (MacKay 1942; Cleaver 1949). Water 

temperatures and changes in water temperatures 

have considerable influence on the rate of egg 

development and mortality after fertilization and 

spawning. When temperatures rise, the rate of 

egg development also rises, but so does the rate 

of mortality. In laboratory tests (Wild 1983) 

eggs held at 9.4 "C hatched in 123 days and at 

16.7 "C they hatched in 64 days. At 10 "C, 

685,000 larvae were produced per egg mass, 

whereas at 16.7 "C, 14,000 larvae were produced 

per egg mass. Egg mortality for eggs from 

Similk Bay, Washington, was 20% after 20 min 

exposure at 10 "C; 30% after 4 min and 90% 

after 20 min at 15 "C; and 100% after 4 min at 

20 "C (Mayer 1973). 

Epibiotic fouling of Dungeness crab eggs has 

been linked to increased egg mortality because 

of mechanical interference with hatching and 

oxygen consumption (Fisher 1976; Fisher and 

Wickham 1976, 1977). Waters with high and 

rising nutrient levels are suspected to cause 

increased fouling. Egg predation by a 

nemertean worm, Carcinonemertes en-am, is 

thought to increase the fouling of eggs through 

the liberation of yolk during its feeding and 

defecation (Wickham 1979a, 1979b). In coastal 

waters near San Francisco, the estimated 

average annual mortality caused by predation of 
the worm on Dungeness crab eggs was over 

55% in 1974-79 when worm densities were 

about 14 per 1,000 eggs (Wickham 1979b). 

Eggs hatch in 2 to 3 months (Cleaver 1949; 

Orcutt 1978; Wild 1983). The hatching season 

commonly shortens from north to south along 

the Pacific coast. Eggs hatch in coastal waters 

from December to June in British Columbia, 

but considerably later in Queen Charlotte 

Islands (MacKay 1942; Butler 1956), from 

January to April in Washington (Cleaver 1949; 

Armstrong et al. 1981), from December to April 

in Oregon (Reed 1%9; Lough 1976), from 

January to early March in northern California 

(Wild 1983), and commonly from late December 

to early February in central California (Wild 

1983). 

Larvae 

Larvae emerge as prezoeae and molt to 

zoeae within about 1 h, but the prezoeal 

period varies with salinity (Buchanan and 

Milleman 1%9). The larvae progress through 

five zoeal stages before molting into megalops 

(Figure 4; Poole 1%6; Reed 1%9; Lough 1976). 

In central California, first stage zoeae appear 

between mid-December and early January, and 

fifth stage zoeae appear between midFebruary and mid-March; about 80-95 days are 

required to complete the five zoeal stages in 

California (Reilly 1985). Zoeae first appear 5- 

16 km from shore (Lough 1976; Orcutt 1977; 

Reilly 1983a). In both central and northern 

California, zoeae are almost always found in the 

ocean, not the bays (Reilly 1985). Of hundreds 

of estuarine samples, only two contained zoeae; 

of several thousand oceanic samples, about 

2,000 contained zoeae (Reilly 1985). Dungeness 

crab larvae appear to be unique among larval 

brachyurans in central California in this respect 

and are the most abundant first stage zoeae 

present at offshore depths greater than 30 m 

(Reilly 1985). All four of the other Cancer 

crabs of central California--the red crab (C. 

productus), the slender crab (C. gracilis), the 

rock crab (C. antennarius), and the yellow crab 

(C. anthonyi)--occur as first stage zoeae in San 

Francisco Bay (Reilly 1985). Offshore 

movement and distribution of Dungeness crab 

larvae are probably regulated by a variety of 

factors, including depth, latitude, temperature, 

salinity, and ocean currents (Reilly 1983a, 1985). 

Multiple regression analysis indicated that depth 

is the most important independent variable that 

is correlated with larval distribution offshore 

(Reilly 1983a, 1985). Distribution is also dependent upon the larval stage, and the larvae show 

a die1 pattern of vertical distribution; they are 

near the surface at night and at depth during 

the day (Reilly 1983a, 1985). Considerable 

ofEshore movement of larvae occurs during the 

zoeal stages; the larvae appear to be transported seaward from the onset of hatching 

(Reilly 1983a). Hatfield (1983) indicated that 

Dungeness crab zoeae appear to move offshore 

and presumably alongshore during late winter 

and the winter-to-spring transition period. After 

upwelling occurs around April and May, the 

megalops (advanced stage) appear in large nearshore concentrations, although the mechanism 

by which they move inshore is unclear. 

The megalops (advanced) stage of the 

Dungeness crab is found from May to 

September off the coast of British Columbia. 

It is the last pelagic stage. In Washington 

coastal waters, the megalopae first appear in 

April; abundance peaks in May through June. 

In Oregon waters, they are most abundant in 

April and May (MacKay 1942; Cleaver 1949; 

Butler 1956; Lough 1976; Stevens 1982). 

Dungeness crabs spend 25-30 days as megalopae 

in California where they first appear in early 

March, but may appear as late as mid-April 

(Reilly 1985). This trend of abundance 

indicates larval development ends later 

proceeding from south to north. Off Oregon, 

megalops are carried within 1 km of shore by 

tidal currents and by self-propulsion (Lough 

1976). Megalopae often are abundant on the 

hydrozoan Velella velella, when they are scarce 

or absent elsewhere in the water column 

(Wickham 197%; Stevens and Armstrong 1985). 

Wickham (197%) suggested that V: velella aids 

in the movement and distribution of megalops 

and possibly provides a food source and 

protection from predation. 

Larvae eat both zooplankton and 

phytoplankton, but zooplankton is most 

important (Lough 1976). The larvae capture 

food items with the natatory hairs of their 
Egg from 

female 

larval crab 

Figure 4. Life cycle stages of the Dungeness crab: Zoea, megolops, postlarva (juvenile), and adult. 

maxillipeds, and size of food is a selection factor 

(Lough 1976; Armstrong et al. 1981). 

Information on larval predators and predation 

rates is scarce. Zoeae are thought to be 

consumed by numerous types of planktivores 

(Stevens 1982); megalopae are preyed upon by 

many fishes, including coho salmon 

(Oncorhynchus butch) and chinook salmon (0. 

tshawytscha), according to Orcutt et al. (1976) 

and Reilly (1983b). Heavy predation by salmon 

may have caused the decline of the Dungeness 

crab catch in the San Francisco Bay area (Reilly 

1983b). There appears to be a direct relationship between coho salmon hatchery production 

in Oregon and the magnitude of predation on 

the megalopae in California waters (Reilly 

1983b). In a study of food habits, the combined 

stomachs of eight coho salmon contained 1,061 

megalops (Orcutt 1977); in a separate study 

(MacKay 1942) up to 1,500 megalopae were 

found in the stomach of a single fish. Prince 

and Gotshall (1976) found Dungeness crab 

megalops and instars, the stages between 

postlarval (including adult) molts, to be the 

most important food of copper rockfish 
(Sebastes caurinus) in northern California's 

Humboldt Bay. 

The abundance of a year class depends in 

part on larval survival to metamorphosis 

(Peterson 1973; Wickham et al. 1976; McKelvey 

et al. 1980). Natural larval mortality is probably 

high because of a combination of predation, 

excessively high or low water temperatures and 

fluctuations, a scarcity or low quality of food, 

and currents affecting distribution (Lough 1976; 

Armstrong 1983). 

Juveniles 

Most megalopae molt into juveniles in August 

off the coast of British Columbia (Figure 4; 

MacKay 1942; Butler 1956), and in April-May 

off the coasts of both Oregon (Lough 1976) 

and Washington (Stevens 1982). After molting, 

the juveniles are found in shallow coastal waters 

and estuaries, and large numbers live in beds of 

eelgrass (Zostera sp.) or other aquatic vegetation that provide protection and substrate and 

harbor food organisms for early instars (Butler 

1956; Orcutt et al. 1975; Stevens and Armstrong 

1984, 1985). Recently, shells of bivalves such as 

the softshell clam (Mya arenaria) and the Pacific 

oyster (Crassostrea gigas) have been documented 

as very important habitat for young Dungeness 

crabs (Armstrong and Gunderson 1985). In 

central California, there is evidence that 

movement of postlarval Dungeness crabs into 

the estuaries takes place in May and June via 

bottom currents, where they stay for 11-15 

months (Tasto 1983). Juveniles are more 

common in estuaries, while subadults and adults 

are more common offshore. The importance of 

estuaries to juvenile Dungeness crabs has been 

discussed in detail (Tasto 1983; Armstrong and 

Gunderson 1985; Stevens and Armstrong 1985; 

Emmett and Durkin 1985). Dungeness crab tag 

recovery data in California show a regular 

pattern of movement of juvenile crabs out of 

estuaries and a random movement of adult 

crabs in the ocean (Collier 1983). Armstrong 

(1985) noted that spawning takes place offshore, 

which would be a major reason for adults 

moving out of the estuaries. 

Juveniles molt 11 or 12 times before sexual 

maturity (Butler 1960, 1961b). Carapace width 

at the first instar (the first benthic stage) varies 

from about 5 mm to greater than 8.5 mm 

(Cleaver 1949; Waldrom 1958; Butler 1960, 

l%lb; Poole 1%7). After 1 year of growth 

beyond hatching, most crabs in Bodega Bay, 

California, are in their 8th, 9th, or 10th instar 

(Poole 1%7). By comparison, crabs from Grays 

Harbor, Washington, only attain the sixth or 

seventh instar by the end of their first year of 

life (Stevens and Armstrong 1984). Carapace 

width (CW) after the first year averages 44 mm 

in Grays Harbor, while the range is 63-94 mm 

in Bodega Bay (Poole 1%7; Stevens et al. 

1982). The crabs mature after about 2 years 

(Butler l%lb) at about 116 mm CW for males 

and 10 rnm for females (Butler 1960). 

The diet of juvenile crabs consists largely of 

fish, mollusks, and crustaceans (Butler 1954; 

Gotshall 1977; Stevens 1982). Juvenile 

Dungeness crabs, 10-30 mm CW, forage for the 

small, estuarine bivalve, Transennella tantilla 

(Asson-Bates 1986). In Grays Harbor, 

Washington, first-year juveniles <60 mm CW 

feed primarily on small mollusks and 

crustaceans. Second-year crabs, 61-100 mm 

CW, feed on fish and prefer Crangon shrimp 

(Stevens et al. 1982). Fish also are important 

to northern California crabs < 10 mm CW 

according to Gotshall (1977), but Butler (1954) 

reported that crustaceans were the primary food 

among crabs of this size in the Queen Charlotte 

Islands, British Columbia. Cannibalism among 

Dungeness crabs has been noted by various 

authors (MacKay 1942; Butler 1954; Tegelberg 

1972; Gotshall 1977; Stevens 1982; Stevens et 

al. 1982). Cannibalism was most prevalent 

among crabs < 60 mm CW which fed on 

smaller crabs of the same year class, probably 

during molting (Stevens 1982; Stevens et al. 

1982). Cannibalism is cited as a possible cause 

of the dramatic population cycles characteristic 

of the Dungeness crab fishery (Botsford and 

Wickham 1978). 

Juveniles are eaten by a variety of demersal 

fishes in the nearshore area, among which the 

most important are various flatfishes--starry 

flounder, Platichthys stellatus; English sole, 

Parophrys vetulus; and rock sole, Lepidopseita 

bilineata (Reilly 1983b). Other predators on 
juvenile crabs are lingcod (Ophiodon elongatus), 

cabezon (Scopaenichthys marnoratus), wolfeels (Anarrhichthys ocellatus), rockfish (Sebastes 

spp.), and octopus (Octopus dofleini), according 

to Waldrom (1958) and Orcutt (1977). Predation on Dungeness crabs may be seasonal in 

nature, as observed in white sturgeons, 

Acipemer transmontanus (McKechnie and 

Fenner 1971). Predation on Dungeness crabs 

may have a devastating impact as in the case of 

sea otters (Enhydra lutrk) in Orca Inlet, Alaska 

(Kimker 1985b). 

Adults 

At about 4 years old, most adult Dungeness 

males in the coastal waters of Washington are 

of marketable size (>I59 mm) (Cleaver 1949; 

Williams 1979). Marketable crabs usually molt 

only once a year (MacKay 1942). The maximum life span of Dungeness crabs is 8 to 10 

years. The maximum size attained is about 218 

mm CW in males and 160 mm CW in females 

at the 16th instar (MacKay 1942; Butler l%lb). 

Adult Dungeness crabs occur primarily in the 

ocean but are also abundant in inland coastal 

waters. Along the coast of northern California, 

legal-sized and large sublegal-sized male crabs 

probably move offshore (often to the south or 

north) in late summer, sometimes through early 

winter; during winter the direction of movement 

is probably reversed and the crabs return 

inshore. Interannual variation in the 

predominant direction of movement is 

considerable (Gotshall 1978b). Collier (1983) 

has shown a random movement of adult crabs 

in the ocean. Many adult female crabs tagged 

off the coast of northern California moved 

relatively little (about 2 km) after 1 year 

(Gotshall 1978b; Diamond and Hankin 1985). 

These tagging studies indicate that adult female 

crabs constitute extremely localized stocks in 

northern California. However, Soule and Tasto 

(1983) reported that Dungeness crabs found in 

different areas along the Pacific Coast exhibited 

low levels of electrophoretic variation, indicating 

that this species dispersed widely and prevented 

local gene differentiation of populations. 

Clams are the most important food of adult 

Dungeness crabs r 151 mm CW in northern 

California (Gotshall 1977) and r 166 mm CW 

in British Columbia (Butler 1954). Crustaceans 

and fish are valuable foods of the adult Dungeness crabs from both Similk Bay and Grays 

Harbor, Washington (Mayer 1973; Stevens et al. 

1982). Dungeness crab populations are 

apparently not limited by the abundance or 

scarcity of particular foods because they are 

nonspecific feeders that readily adjust to various 

foods (Gotshall 1977). They have developed a 

feeding preference for biota on mud-sand 

substrate (Lawton and Elner 1985). 

Crabs of different ages or sizes tend to eat 

different sizes or kinds of food (Stevens 1982; 

Stevens et al. 1982). According to Stevens et 

al. (1982), crabs progress from eating bivalves 

their first year after settlement, to eating shrimp 

(Crangon spp.) their second year, and finally to 

eating juvenile teleost fish in the third year; 

these shifts may be caused purely by changes in 

mechanisms of food handling, or they may have 

evolved to reduce competition among age 

groups of crabs. Crabs display a definite die1 

activity; they are more abundant by day in the 

subtidal area and more abundant at night in the 

intertidal area; the response is positively 

correlated with food availability (Stevens et al. 

1984). Cannibalism is common among adults, 

but no correlations have been made between 

the rate of cannibalism and abundance (Stevens 

1982; Stevens et al. 1982). 

GROWTH CHARACTERISTICS 

In Dungeness crabs, like other crustaceans, 

growth proceeds in steps through a series of 

molts. The general process of crustacean growth 

has been described by Barnes (1974) and 

Warner (1977). The number of molts that a 

crab undergoes before becoming mature 

depends upon the growth increment at each 

molt and the frequency of molting, both of 

which vary among crabs at different locations. 

Dungeness crabs grow in carapace size at each 

molt and gain biom ss between molts. In older 

crabs the growth, a measured by the percent 

change in carapace width, declines as the 

frequency of molting slows down, but the rate 

of weight gain increases over time. The probability of annual molting in female Dungeness 
crabs declines from about 1.0 for crabs of 130- 

135 mm CW to 0.0 for crabs of 155 mm CW 

and larger (Hankin et al. 1985). 

Among possible attributes of estuarine 

residence suggested by Stevens and Armstrong 

(1984) is an enhanced growth rate compared to 

that of siblings of a year class that settle offshore. Size attained by juvenile crabs within 

certain periods after metamorphosis seems to be 

somewhat dependent on latitude and on time of 

settlement. Upper estimates of age at sexual 

maturity range from 4-5 years in British 

Columbia (MacKay and Weymouth 1935) to 1 

year in San Francisco Bay, where the crabs 

reach by this time a carapace width (100 mm) 

usually associated with sexual maturity (Tasto 

1983). More generally, crabs are predicted to 

reach maturity at the end of their second year 

after metamorphosis or in their third growing 

season over much of the coast (Butler l%lb; 

Cleaver 1949). While age and size at sexual 

maturity may not differ substantially along the 

coast, estimates of growth rates of newly settled 

age 0+ crabs do. 

Several studies of juveniles indicate that 

growth rate is accelerated in estuaries or within 

nearshore coastal embayments where water 

temperatures are relatively high (Stevens and 

Armstrong 1984; Armstrong and Gunderson 

1985). This difference in growth rate may be 

due to a temperature difference which is 

approximately 6 "C higher in the estuary than 

the ocean (Armstrong and Gunderson 1985). 

Growth of young-of-the-year crabs is 

substantially slower offshore from San Francisco 

Bay, in the Gulf of the Farallons, than in 

estuaries (Tasto 1983), where the offshore 

crabs are about 28-30 mm and those in the 

estuary are about 60 mm in width. Gulf-reared 

crabs require about 2 years after metamorphosis 

to reach the first postlarval instar width of 100 

mm, while the average bay-reared crab reaches 

this size one year after metamorphosis (Tasto 

1983). 

Growth of California Dungeness crabs is 

somewhat faster in males than females (Figure 

5), but varies from year to year and among 

geographic regions (Tasto 1983). In northern 

Figure 5. Mean carapace width of male and 

female crabs from central California, 1977-80. 

115 - 110 - 105 - 100 - rn - 

4) - 85 - 

e4 - 

75 - - 

rm- 

- 65 - E 

_OMZ 

u 55 - 2 so - = 5 45 - 40 - 35 - YI - I5 - m. 

I5 - 

'a - 5 - 

California, age and growth are similar to that 

observed in Washington, where crabs become 

fully recruited into the fishery at 4 years of age, 

having reached a carapace width of about 

159 mm (Warner 1985b; 1987). Dungeness crab 

growth is variable along the Pacific coast. 

However, in general, it is somewhat slower in 

the northern part of the range (Washington and 

British Columbia) when compared to the 

southern part of the range (California). 

*IF MF MF MF MF MF MF MF UF MF MF MF 

JUN JUL AUG SEP OCT NOV DEC JAN Fin MAR APR MAY 

THE FISHERY 

Commercial landings of Dungeness crab on 

the Pacific coast have fluctuated widely, almost 

cyclically, over the past 30 years (Figure 6) and 

have been reviewed by Armstrong (1983). The 

cyclical characteristics of the catches were most 
4 BRITISH COLUMBIA 

V) 

WASHINGTON 

15- 

5- 

I 

1955' 57 59 61 '63 65 67 69 71 73 75 77 

I I I 1 I 1 I I I I d 

- 

25 - CALIFORNIA 

- 

15- 

5 - 

Figure 6. Dungeness crab landings by season in Pacific Coast States and in the Province of Br 

Columbia, 1955-83. 
noticeable in northern California (Gotshall 

1978a; Farley 1983; Dahlstrom and Wild 1983; 

Warner 1985a). Several hypotheses have been 

proposed to explain the cyclic nature of 

Dungeness crab population size. According to 

Peterson (1973), commercial landings were 

highest 1.5 years after a period of strong upwelling in California and Oregon, and 6 months 

following a strong upwelling in Washington, 

although the biological sense of such a relation 

is much in doubt. Botsford and Wickham 

(1975) challenged this conclusion by using autocorrelation to show that commercial landings are 

cyclic but that strong upwelling is not. 

Another hypothesis to explain catch fluctuations suggests that periods of high levels of 

cannibalism and interspecific competition may 

cause a decline in the fishery 3 or 4 years later 

(Botsford and Wickham 1978). In a model 

predicting recruitment, McKelvey et al. (1980) 

discounted cannibalism as a factor and 

contended that changes in egg and larval survival regulate population success. Larval 

survival may be seriously reduced by a 

combination of environmental factors that can 

cause increased mortality if unfavorable for even 

short periods of time (Lough 1976). Stevens 

and Armstrong (1981) indicate that diseases 

caused by various organisms (bacteria, Protozoa, 

or fungi) may be responsible for mass 

mortalities of adult crabs. Predation may have 

a profound impact on the Dungeness crab 

commercial fishery in certain geographic areas 

(Kimker 1985b). Reilly (1983b) hypothesized 

that extensive predation by hatchery-released 

coho salmon from the Columbia River continually suppressed the Dungeness crab fishery. 

There is an apparent cyclic covariance between 

abundance of salmon and Dungeness crabs 

(Botsford et al. 1982). 

Dungeness crab landings from 1954 to 1983, 

divided by State and Province (Figure 6), show 

that landings in Washington (except Puget 

Sound), Oregon, and California generally 

followed similar trends. Landings from Puget 

Sound and British Columbia are lower and show 

less annual variation. Alaska landings bear little 

relation to other areas of the Pacific Northwest. 

Recent reviews of the commercial Dungeness 

crab fishery have been published for Alaska 

(Eaton 1985; Kimker 1985b; Koeneman 1985; 

Merritt 1985), British Columbia (Jamieson 

1985), Washington (Barry 1985), Oregon 

(Demory 1985), and California (Dahlstrom and 

Wild 1983; Warner 1985a). 

California has five commercial Dungeness 

crab fishing areas: (1) Eureka to Crescent City; 

(2) Fort Bragg; (3) San Francisco to Bodega 

Bay; (4) Monterey; and (5) Avila Bay to Morro 

Bay (Figure 2). The commercial fshery extends 

south to Point Conception. Two major populations of Dungeness crabs are commercially 

exploited in California (Warner 1985a)--those 

from northern California and those from central 

California (Figures 2 and 7). Point Arena is 

the division between these two fisheries, 

according to Farley (1983). Central California 

catches have been low since about 1%2 (Figure 

7), whereas in northern California good catches 

for about 6 years have alternated with poor 

catches of about 4 years (Figure 7). Crescent 

City has been the major port of landing in 

California (Warner 1985a). 

Only male crabs 6-114 inches wide or wider 

may be taken commercially in California. Not 

more than 1% of any catch may be smaller than 

this size and no crabs less than 5-314 inches may 

be retained (Warner 1985a). Most crabs taken 

in the California commercial fishery are 4-yearolds, although some 3- and 5-year-old crabs are 

taken (Warner 1985a). 

Figure 7. Dungeness crab landings for central 

and northern California (Farley 1983). 

e" - 

f 

0 C - L 

- Central California 4 

....-- Northern California o I 

8, 

: : t , 1, I I 

# I 

I. I I 

I, 

, . 8. 

I . -___- * 

I I 

1949-50 54-55 59-60 64-65 69-70 74-75 78-79 
Sport catch data are scarce and according to 

Barry (1985) the Washington sport fishery on 

Dungeness crabs amounts to less than one 

percent of the annual commercial harvest. 

Most of the available sport catch data are from 

a survey reported by Williams (1979). He 

revealed that from April through August 1974, 

471 crabs were taken intertidally at Mission 

Beach, Washington, by 735 sport crabbers. 

April, May, and June produced the best sport 

catches, with the highest average catches 

occurring on low tides that ranged from -0.60 to 

-0.74 m. Aerial surveys made over Puget Sound 

beaches using Williams' (1979) survey data estimated that the beaches of Washington State 

probably supported about 20,000 crabbers during 

those months in 1974. In 1975 in Washington, 

the sport crab pot fishery alone accounted for 

the harvest of about 300,000 Dungeness crabs 

(Tegelberg 1976). Other sport catch methods 

are ring nets, dip nets, and hook and line. 

Although both male and female crabs may be 

taken in the California sport fishery (Figure 3), 

there is a minimum size for both sexes of 6-114 

inches, measured in front of the 10th 

anteriolateral spines. The daily catch limit is 10 

crabs. Concern over the excessive take of 

sublegal sized Dungeness crabs in the sport 

fishery prompted the California Fish and Game 

Commission in 1978 to close the fishery in San 

Francisco and San Pablo Bays inside Golden 

Gate (Dalstrom and Wild 1983). Sport fishing 

for Dungeness crabs is most active in the 

Crescent City area (Dalstrom and Wild 1983). 

Nearly 4 times more red crabs (C. productus) 

than Dungeness crabs are taken in the sport 

fishery. Rock crabs, slender crabs, and yellow 

crabs are also taken in the sport fishery in 

limited numbers. 

A useful publication for sport crabbers in 

California by Phillips (1973) describes the 

common members of the genus Cancer and the 

gear used to catch them. 

ECOLOGICAL ROLE 

Dungeness crabs consume a wide variety of 

food organisms and are prey to numerous 

predators. Crabs contribute to several trophic 

levels as they progress through successive life 

stages. The larvae largely consume plankton 

(Lough 1976) and are preyed upon by 

numerous fshes. Adults and juveniles are 

preyed upon by sea otters, fshes, and octopuses 

(Butler 1954; Waldrom 1958; Stevens 1982; 

Reilly 1983b; Kimker 1985b). Cannibalism is 

common and probably exercises some control 

over abundance. In their various life stages, 

Dungeness crabs feed on a variety of mollusks, 

crustaceans, and fsh species (Stevens et al. 

1982). Other information on the ecological role 

is given in the life history section. 

ENVIRONMENTAL REQUIREMENTS 

The temperature preferences of adult crabs 

are different among seasons (Mayer 1973). 

They are somewhat tolerant of abrupt temperature and salinity fluctuations (Cleaver 1949) 

and water temperatures from 3 to 19 "C were 

listed as normal for the Dungeness crab 

(Cleaver 1949). 

Dungeness crabs have different optimal water 

temperatures at different stages. In the 

laboratory, Des Voigne (1973) reported that 

optimal water temperatures for mating ranged 

from 12 to 16 "C during long photoperiods. 

Wild (1983) noted an apparent trend towards 

crabs mating later in colder water in his 

laboratory experiments, and noted that mating 

took place between 10 and 17 "C. Other 

factors that were not controlled may have 

interacted with temperature to produce Des 

Voigne's (1973) and Wild's (1983) results. In 

Washington coastal waters, where Dungeness 

crabs usually mate in early spring, when the 

bottom temperatures are between 8 and 10 "C 

(Armstrong, unpubl. data). Reported spawning 

temperatures vary partly because they are not 

based on well-managed experiments. According 

to Wild (1983), the egg brooding periods varied 

ii~versely with seawater temperatures of 9 to 

17 "C (Figure 8). Moving northward along the 

Pacific coast, prolonged egg brooding periods in 

colder water are consistent with prolonged 

occurrences of ovigerous crabs and cooler ocean 
Figure 8. Egg-brooding periods of the 

Dungeness crab at various laboratory seawater 

temperatures. 

130 

- I20 

V) 

3 110 

8 

5 KY) ' 90 P * 80 

U 

m 

m 

temperatures (Wild 1983). Hatching success, 

considered as the number of larvae that hatch 

from an egg mass, decreased as the temperature 

increased from 10 to 17 "C (Wild 1983). Mayer 

(1973) found a similar correlation between egg 

mortality and temperature with 20% mortality 

after 20 min at 10 "C and 100% mortality after 

4 min at 20 "C. 

'I 

. 4 . .* 

*J 

- 

- a. 

9 10 11 11 13 Id 15 16 17 

Optimal temperatures for larvae are 10 to 

14 "C. Juvenile crabs, 80 mm wide and 

acclimated to 10.0 "C, have been exposed to 

water temperatures up to 25.0 "C for 7 days 

with little or no mortality (Des Voigne 1973); 

however, an increase to 27.5 "C was fatal to 

100% of all crabs tested. In the laboratory, 

adult crabs had a maximum tolerable temperature of 25 "C during long photoperiods, 

which decreased to 20 OC when exposed to 

short photoperiods (Des Voigne 1973). With 

adult crabs held for 8 months, Wild (1983) 

observed that mortality increased with 

temperature from 17% at 10 "C to 58% at 

13 "C and to 80% at 17 "C, although laboratory 

stress probably exacerbated the effect of high 

temperatures. 

TEMP 'C 

Salinity 

Tolerance to salinity varies among the life 

stages of the Dungeness crab. In general, 

salinity is not as important as temperature to 

egg development and hatching, but the larvae 

are highly sensitive to changes in salinity 

(Buchanan and Milleman 1969). The percentage of eggs hatching was optimum at 15 ppt, 

but hatching occurred to some degree over a 

wide range of salinities between 10 ppt and 32 

ppt (Buchanan and Milleman 1969). When 

salinity was increased from 15 ppt to 32 ppt, the 

average prezoeal period was reduced from about 

60 min to less than 11 min. At a salinity of 10 

ppt, no prezoeae molted to zoeae, but 100% 

molted at 30 ppt (Buchanan and Milleman 

1969). The highest survival for larvae was 

between salinities of 25 ppt and 30 ppt (Reed 

1969). Survival decreased with salinity and was 

poorest at salinities of 15 ppt; salinities lower 

than 15 ppt are also lethal (Reed 1969). 

Sugarman et al. (1983) demonstrated that adult 

Dungeness crabs close (by retracting their 

appendages and tightly closing their buccal 

cavity) and stop all overt activity to prevent 

ionic exchange at 36.2 ppt (upper limit) and at 

15.5 ppt (lower limit). 

Tempemhue-Salinity Interactions 

Salinity and temperature are both related to 

larval survival. Significant interaction exists 

between these two factors, with salinity 

buffering the effects of temperature. At 

favorable temperatures, unfavorable salinities 

resulted in complete mortality of adults, but 

favorable salinities at unfavorable temperatures 

allowed some survival (Reed 1969). The most 

obvious effect on growth rate occurred at 

temperatures that resulted in the best survival. 

Salinities that favored survival generally had 

little effect on meal growth. Survival of zoeae 

is optimal between the water temperatures of 

10.0 and 13.0 "C and salinities of 25 and 30 

ppt (Reed 1969). The significant interaction 

between temperature and salinity dictates 

caution when making statements about either 

variable independent of the other one. The 

effects of temperature or salinity alone on C. 

magkter zoeae do not appear to cause large 
fluctuations in meal survival in the ocean (Reed 

1969; Lough 1976). 

Adult crabs are found living over several 

substrate types (Schmitt 1921; Cleaver 1949; 

Butler 1956), but they prefer sandy-mud 

bottoms (Karpov 1983; Lawton and Elner 1985). 

Early juveniles prefer beds of eelgrass, shell, or 

sandy mud (Stevens and Armstrong 1984). This 

preference may stem from an abundance of 

food organisms on such substrates or perhaps 

the crabs find shelter from predation there 

(Stevens 1982). Older crabs seem less dependent on epibenthic cover and can be found 

over more exposed substrates. Most crabs 

remain in the subtidal environment, but may 

venture into littoral areas at high tide (Stevens 

et al. 1984). The presence of preferred food 

items enhances this behavior, while low salinities following heavy rains decrease it. 
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Dungeness crab, Cancer magister, with 

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292. 
4. Title and Subtitle 1 5. Report Date 

Species Profile: Life Histories and Environmental Requirements of Coastal Fishes / December 1989 

and Invertebrates (Pacific Southwest)--Dungenas Crab 

50272 -101 

7. Author(%) 8. Performing Organization Rept. No. 

G.B. Pauley, D.A. Armstrong, R. Van Citter, and G.L. Thomas 

REPORT DOCUMENTATION I 1. REmRT NO. 1 2. 

PAGE I Biological Report 82(11.121)* ~ 

I 

9. Performing Organization Name and Address 10. Proiec(lTasklWork Unlt No. 

3. Rec~p~ent's Accessron No 

I 

IS. Supplementary Notes 

, *U.S. Army Corps of Engineers Report No. TR EL-82-4 

U.S. Department of the Interior U.S. Army Corps of Engineers 

Fish and Wildlife Service Waterways Experiment Station 

Research and Development P.O. Box 631 

National Wetlands Research Center Vicksburg, MS 39180 

1 16. Abstract (Limit: 200 words) I 

11. Contract(C) or Grant(C) NO. 

(c) 

(GI 

Species profiles are literature summaries of the taxonomy, life history, and environmental requirements 

of coastal aquatic species. They are designed to assist in environmental impact assessments. The 

Dungeness crab (Cancer magister) is found in California estuaries and off the coast of California. It 

is a shellfish highly prized and sought after by both commercial and sport fishermen. Commercial 

landings in California have fluctuated widely, almost cyclically, over the past 30 years. In the California 

Washington, DC 20240 - 

12. Sponsor~ng Organlzatlon Name and Address 

sport fihery, a minimum size of 6.25 inches carapace width has been established. Dungeness crab 

have a life cycle that involves several metamorphic stages: zoea, megalops, postlarval crab, and adult 

crab. Normal temperatures for Dungeness crabs are 3 to 19 OC. Optimum salinity for egg hatching 

is about 15 ppt, but the survival rate of larvae is highest at salinities of 25 to 30 ppt. 

17. Document Analysis a. Descridon 

Estuaries Temperature Growth 

Fisheries Feeding habits Sediments 

Crabs Life cycles Depth 

Salinity 

b. IdentlfienlOpen.Ended Terms 

Dungeness crab Life history 

Cancer magister Environmental requirements 

c. COSATI FialdlGroup 

la Avallabtlity Statement 1 19. Securgty Class (This Report) 

Unlimited Distribution 1 Unclassified I 20. Secur~ty Class (This Page) 1 Unclassified 

21. No. 3f Pages 

20 

22. Price 

I 

(See ANSI-Z39.18) OPTIONAL FORM 272 (4-77) 

(Formerly NTIE35) 

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the Interior has responsibility for most of our nationally owned 

public lands and natural resources. This includes fostering the 

wisest use of our land and water resources, protecting our fish 

and wildlife, preserving the environmental and cultural values of our 

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our energy and mineral resources and works to assure that their 

development is in the best interests of all our people. The Department also has a major responsibility for American Indian reservation 

communities and for people who live in island territories under U.S. 

administration. 

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