Abstract. — During 1987 and 

 1988, sea otter, Enhydra lutris, 

 prey composition and foraging suc- 

 cess were studied by observing for- 

 aging otters in the northern Kodiak 

 Archipelago. Study areas differed 

 in the number of years in which 

 they were occupied by sea otters 

 and were categorized as estab- 

 lished (occupied >25 years), inter- 

 mediate (occupied 5-15 years), and 

 frontal (occupied <5 years). Clams 

 were the most frequently identified 

 sea otter prey (57-67%) in all study 

 areas, and of the clams identified 

 to species, Saxidomus giganteus 

 was the most frequently observed. 

 Mussels, Mytilus spp., crabs (primar- 

 ily Telmessus spp.), and green sea 

 urchins, Strongylocentrotus droe- 

 bachiensis, contributed <25% to the 

 total prey within each study area. 

 Adults did not differ in the propor- 

 tion of clams, mussels, or crabs cap- 

 tured as prey among study areas. 

 Adults captured clams with a greater 

 frequency and mussels with lesser 

 frequency than did juvenile sea ot- 

 ters for all study areas combined. 

 Forage success did not differ among 

 study areas for adults nor between 

 adults and juveniles for all study 

 areas combined. Adult sea otters in 

 the established area appear to have 

 compensated for reduced prey size by 

 retrieving more prey items per dive; 

 however, they obtained less clam bio- 

 mass per dive than otters in the in- 

 termediate and frontal areas. 



Sea otter, Enhydra lutris, prey 

 composition and foraging success 

 \n the northern Kodiak Archipelago 



Angela M. Doroff 



U.S. Fish and Wildlife Service, Alaska Fish and Wildlife Research Center 

 1011 East Tudor Road. Anchorage. Alaska 99503 



Present address: U.S. Fish and Wildlife Service. Marine Mammals Management 



1011 E Tudor Road. Anchorage, Alaska 99503 



Anthony R. DeGange 



US Fish and Wildlife Service, Alaska Fish and Wildlife Research Center 

 1011 East Tudor Road, Anchorage, Alaska 99503 



Present address U S Fish and Wildlife Service, Ecological Services 



1011 East Tudor Road, Anchorage, Alaska 99503 



Manuscript accepted .31 March 1994. 

 Fishery Bulletin 92:704-710 ( 1994). 



704 



The Kodiak Archipelago in south- 

 central Alaska (Fig. 1) supported an 

 abundant sea otter, Enhydra lutris, 

 population prior to their commercial 

 exploitation during the 18th and 

 19th centuries (Lensink, 1962; 

 Kenyon, 1969). Following this pe- 

 riod of unregulated harvesting of 

 sea otters, which was terminated in 

 1911 (Kenyon, 1969), an isolated 

 remnant population of sea otters 

 remained at the northern tip of 

 Shuyak Island (Schneider 1 ). During 

 the late 1950s through mid 1980's, 

 episodic range expansion occurred 

 throughout the northern Kodiak 

 Archipelago (Lensink, 1962; Schnei- 

 der 1 ; Simon-Jackson et al. 23 ). 



In the absence of sea otters, dense 

 populations of clams, crabs, sea ur- 

 chins, and abalones may develop. As 

 sea otters recolonize former habitat, 

 shellfish densities decrease owing to 

 sea otter predation, sometimes in 

 combination with commercial and 

 subsistence shellfish harvest 

 (Garshelis et al., 1986). Sea otters 

 have been implicated in closure of 

 commercial and recreational fisher- 

 ies in California for abalone, Hal- 

 iotis spp. (Estes and VanBlaricom, 

 1985) and pismo clams, Tiuela stul- 

 torum, (Stephenson, 1977; Miller et 

 al. 4 ). In Alaska, sea otters impacted 



the recreational and commercial 

 fisheries for Dungeness crab, Can- 

 cer magister, in Prince William 

 Sound (Garshelis, 1983; Garshelis 

 etal., 1986; Kimker 5 ). 



During 1987-1988 the sea otter 

 range continued to expand near 

 southeastern Afognak Island of the 

 Kodiak Archipelago. The natural 

 recolonization pattern of the archi- 

 pelago provided an opportunity to 

 study the effects of sea otters on 



Schneider, K. B. 1976. Assessment of the 

 distribution and abundance of sea otters 

 along the Kenai Peninsula. Kamishak Bay 

 and the Kodiak Archipelago. U.S. Dep. 

 Commer., NOAA, OCSEAP Final Rep. 

 37:527-626. 



'■ Simon-Jackson, T., D. Taylor, S. Schliebe 

 and M. Vivion. 1985. Sea otter survey, 

 Kodiak Island-1984. U.S. Fish and Wild- 

 life Service, Anchorage, Alaska. Unpubl. 

 rep., 16 p. 



; Simon-Jackson, T., M. Vivion, and D. 

 Zwiefelfofer. 1986. Sea otter survey, 

 Kodiak Island-1985. U.S. Fish and Wild- 

 life Service, Anchorage, Alaska. Unpubl. 

 rep., 11 p. 



Miller, D. J., J. E. Hardwick, and W. A. 

 Dahlstrom. 1975. Pismo clams and sea ot- 

 ters. Calif. Dep Fish and Game. Mar. Re- 

 sources Tech. Rep. 31:1-49. 

 Kimker, A. 1985. A recent history of the 

 Orca Inlet, Prince William Sound Dunge- 

 ness crab fishery with specific reference to 

 sea otter predation. In B. R. Metleffled.), 

 Symposium on Dungeness crab biology and 

 management, p. 231-241. Univ. of Alaska, 

 Alaska Sea Grant Rep. 85-3. 



