FEEDING BEHAVIOR AND MAJOR PREY SPECIES OF 



THE SEA OTTER, ENHYDRA LUTRIS, IN MONTAGUE STRAIT, 



PRINCE WILLIAM SOUND, ALASKA 



Donald G. Calkins' 



ABSTRACT 



Food habits and feeding behavior of sea otters were studied in Prince William Sound, Alaska, from May 

 through August 1971. Otters fed primarily on clams, crabs, and sea stars: Saxidomus gigantea, 

 Telmessus cheiragonus, and Evasterias troschelii, respectively, were the most important prey species 

 identified in the major groups. Mean times for feeding dives were 67 s for females (mean water depth = 

 9.6 m) and 59 s for males (mean water depth = 11.9 m). Clams were dug from the bottom and opened 

 with the aid of stones. Sea urchins and fishes were not identified as dietary components. 



The sea otter, Enhydra lutris, hunted to near ex- 

 tinction by 191 1 in Alaska, is steadily reoccupying 

 its former range. Several areas are being repopu- 

 lated naturally (Kenyon 1969), while others have 

 been restocked with otters translocated from Am- 

 chitka Island in the Aleutians or from south cen- 

 tral Alaska (Burris and McKnight 1973). In some 

 areas of the Aleutian Islands, sea otters have be- 

 come so abundant that an experimental harvest 

 has been conducted by the Alaska Department of 

 Fish and Game. Populations in Prince William 

 Sound have become large enough to permit cap- 

 ture of a small number of animals for restocking 

 areas of former abundance. 



Large gaps still exist in our knowledge of the 

 biology and life history of the sea otter. Past 

 studies have dealt primarily with populations 

 along the California coast and off Amchitka Is- 

 land. No intensive study of sea otters in Prince 

 William Sound has been completed, and the only 

 available information from that area concerns re- 

 stocking activities and population counts (Pitcher 

 and Vania^). The lack of information on the biol- 

 ogy of the sea otter in Prince William Sound and 

 the impending development of oil reserves along 

 the Alaska coast motivated this study. 



STUDY AREA 



This investigation took place in Montague 

 Strait, Prince William Sound, Alaska (Figure 1). 



^Alaska Department of Fish and Game, 333 Raspberry Road, 

 Anchorage, AK 99502, 



^Pitcher, K. W., and J. S. Vania. 1973. Distribution and abun- 

 dance of sea otters, sea lions and harbor seals in Prince William 



One week was spent in the field in September 

 1970. In May 1971, a camp was established at the 

 northwestern end of Montague Island (lat. 

 60°15'54"N, long. 147°12'18"W). Observations 

 were made from May through August 1971. The 

 study area included the northwestern end of Mon- 

 tague Island, from Stockdale Harbor to a logging 

 camp 19 km southwest. Green Island, Little Green 

 Island, and the adjacent waters were also included 

 (see Figure 1). 



The area was selected as a location where sea 

 otter populations have always existed. Although 

 the population is still expanding, there has always 

 been some sea otters in this area (Karl Schneider, 

 Alaska Department of Fish and Game, pers. com- 

 mun.). 



The area is characterized by a rugged coastline 

 with rocky shores. Two sand beaches occur in the 

 area, one south of Port Chalmers and one on the 

 south side of Green Island. Several streams empty 

 into the Sound from Montague Island: mud flats 

 and small estuaries are common. The mud flats 

 support stands of eel grass, Zostera sp., and pro- 

 vide habitats for populations of clams — Macoma 

 spp., Saxidomus gigantea, and Protothaca 

 staminea. 



Approximately 55 km of coastline was included 

 in the study area. Kenyon (1969:57) stated that 

 "generally sea otters favor waters adjacent to 

 rocky coasts near points of land" and that "coasts 

 adjacent to extensive areas of underwater reefs 

 are particularly attractive." Using these criteria, 



Manuscript accepted June 1977. 



FISHERY BULLETIN: VOL. 76, NO. 1, 1978. 



Sound. Unpubl. manuscr., 18 p. Available Alaska Department of 

 Fish and Game, Anchorage, Alaska. 



125 



