mates of 4-6 mo gestation periods, which assume 

 that copulation and conception do not occur until 

 after weaning, seem reasonable if the blastocyst is 

 implanted soon after conception, partially skip- 

 ping or entirely skipping the delay period. Our 

 field data and that from captive studies indicate 

 that the gestation period in sea otters may be 

 variable and depend on an external stimulus or 

 the general well being of the female. 



Literature Cited 



ANTRIM, J. E., AND L. H. CORNELL. 



1980. Reproduction of the sea otter Enhydra lutris in 

 captivity. Int. Zoo Yearb. 20:76-80. 

 BARABASH-NIKIFOROV, I. I. 



1935. The sea otters of the Commander Islands. J. 



Mammal. 16:225-261. 

 1969. The Russian sea otter Animals, p. 156-158. Vol. 12. 



Brosseau, C, M. L. Johnson, a. m. Johnson, and K. W. 

 kenyon. 



1975. Breeding the sea otter, Enhydra lutris, at Tacoma 

 Aquarium. Int. Zoo Yearb. 15:144-147. 



Kenyon, K. w. 



1969. The sea otter in the eastern Pacific Ocean. No. Am. 

 Fauna 68, 352 p. 

 LENSINK, C. J. 



1962. The history and status of sea otters in Alas- 

 ka. • Ph.D. Thesis, Purdue Univ., Lafayette, 188 p. 

 LOUGHLIN, T. R. 



1977. Activity patterns, habitat partitioning, and groom- 

 ing behavior of the sea otter, Enhydra lutris, in Califor- 

 nia. Ph.D. Thesis, Univ. California, Los Aug., 110 p. 



Sandegren, F. E., E. W. Chu, and J. E. Vandevere. 



1973. Maternal behavior in the California sea otter J. 

 Mammal. 54:668-679. 



Sinha, A. A., C. H. Conaway, and k. W. Kenyon. 



1966. Reproduction in the female sea otter J. Wildl. 

 Manage. 30:121-130. 



Vandevere, J. E. 



1972. Behavior of southern sea otter pups. Proc. Ninth 

 Annu. Conf Biol. Sonar and Diving Mamm., p. 21-35. 



THOMAS R. LOUGHLIN 



Northwest and Alaska Fisheries Center 

 National Marine Fisheries Service, NOAA 

 7600 Sand Point Way NE 

 Seattle, WA 98115 



Marine Resources Branch 



California Department of Fish and Game 



2201 Garden Road 



Monterey, CA 93940 



Jack a. Ames 



Judson E. Vandevere 



93 Via Ventura 

 Monterey, CA 93940 



MASS MORTALITY OF FEMALE 



DUNGENESS CRAB, CANCER MAGISTER, 



ON THE SOUTHERN WASHINGTON COAST 



Studies of growth and age of Dungeness crab, 

 Cancer magister, populations from California to 

 British Columbia have amply elucidated devel- 

 opmental rates for this species (Cleaver 1949; Wal- 

 dron 1958; Butler 1961; Poole 1967), but no infor- 

 mation is contained in such reports on mortality 

 and its causes, apart from reference to known 

 predators and cannibalism. Natural mortality for 

 highly mobile crustaceans is difficult to investi- 

 gate because animals simply do not expire in eas- 

 ily observed locations or are quickly removed by 

 scavengers once dead. Consequently, there has 

 been no documentation of extensive crustacean 

 mortality by causes such as disease or pollution on 

 the Pacific coast of the United States, and there- 

 fore loss from a population throughout its life cycle 

 due to a generalized predator category (including 

 fishing and cannibalism for C. magister, Botsford 

 and Wickham 1978) remains the traditional mor- 

 tality component of the literature on many crusta- 

 ceans including Dungeness crabs. 



On 18 April 1979 large numbers of dead Dunge- 

 ness crabs on the beach at Grayland, Wash. (Fig- 

 ure 1), were reported to the Westport Field Office of 

 the Washington Department of Fisheries (WDF). 

 Inspection of the beach between Westport and the 

 northern end of Willapa Bay confirmed that many 

 Dungeness crabs had been washed ashore and, 

 contrary to our initial supposition, were not 

 exuvia which are often mistaken for dead crabs by 

 the public. Preceding this instance, we had reports 

 of dead crabs in the pots of commercial fishermen 

 in Willapa Bay in February 1979, and these find- 

 ings were verified by WDF personnel. 



In response to the report of 18 April, five locales 

 on the beach from Grays Harbor to Willapa Bay 

 (Figure 1, Table 1) were quantitatively examined 

 for dead crabs and the shoreline between these 

 points was inspected from a car. All crabs along the 

 five transects were counted and sexed, if possible, 

 and 42 Dungeness crabs at transect 3 were mea- 

 sured to the nearest millimeter across the 

 carapace inside the tenth anterolateral spines. 



Results 



Dead crabs found on the beach between Grays 

 Harbor and Willapa Bay were confined to the line 

 of previous high tide in a swath about 8-10 m wide. 



FISHERY BULLETIN: VOL. 79, NO. 2, 1981. 



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