A small group of northern fur seals (Callorhinus ursinus) including one male with two females, each with a small pup, and two lone males were discovered on Bogoslof Island, Alaska in the Bering Sea on 20 July 1980. This is the first evidence of breeding on Bogoslof, or on any island in the eastern Bering Sea other than the Pribilof Islands. We suggest that these fur seals require breeding islands adjacent to the continental shelf break where they are supported by the pelagic food web characteristic of the oceanic and outer shelf domains.Key words: fur seal, Callorhinus ursinus, Steller sea lion, Eumetopias jubatus, Aleutian Islands, Bering SeaMots cl&eacute;s: otarie &agrave; fourrure, Callorhinus ursinus, otarie, Eumetopias jubatus, &icirc;les Al&eacute;outiennes, mer de B&eacute;rin

Day, Robert H.

Lloyd, Denby S.

McRoy, C. Peter

English

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VOL. 3 4 ,  NO. 4 (DECEMBER 1981), P. 318-320 ARCTIC Discovery of Northern  Fur Seals (Callorhinus  ursinus) Breeding on Bogoslof Island,  Southeastern Bering Sea DENBY S. LLOYD’, C. PETER McROY’  and  ROBERT H. DAY’ ABSTRACT. A small group of northern fur seals (Callorhinus  ursinus) including one male  with two females, each with a small pup, and two lone males  was discovered on Bogoslof Island, Alaska in the Bering Sea on 20 July 1980. This is the first evidence of breeding on Bogoslof, or on any island in the eastern Bering Sea  other than the Pribilof Islands. We suggest that these fur seals require breeding islands adjacent to the continental shelf break where they are supported by the pelagic food web characteristic of the oceanic and outer shelf domains. Key words: fur seal, Callorhinus  ursinus, Steller sea lion, Eumetopias jubatus, Aleutian Islands, Bering Sea RBSUMÉ.  Le 20 juillet 1980, un petit groupe d’otaries à fourrure (Callorhinus  ursinus), y compris un  mhle et deux femelles, chacune accompagnke d’un jeune  otarie, et deux mgles solitaires, ont kté dkcouverts sur l’île Bogoslof, en Alaska, dans la mer de Bkring.  Ce groupe reprksente la premitre instance d’accouplement sur l’île  Bogoslof ou sur  toute  autre île dans l’est de la mer de Béring, àpart les îles Pribilof. Nous proposons que ces otaries à fourrure nkcessitent des îles d’accouplement adjacentes à la faille  du plateau continental oh ils sont supportks par le reseau alimentaire pélagique caractkristique des domaines océaniques et des plateaux extérieures. Mots cles: otarie à fourrure, Callorhinus  ursinus, otarie, Eumetopias jubatus, îles Alkoutiennes, mer de Bkring Traduit par Maurice Guibord, Department of Archaeology, University of Calgary. INTRODUCTION Our discovery of a  group of northern fur seals (Cablorhinus ursinus Linneaus) apparently breeding on Bogoslof Island in the southeastern Bering Sea, together with reports of new breeding colonies in other  areas, indicate that the species is expanding its choice of breeding sites. The northern fur seal is  known to breed on only a few isolated islands in the North Pacific  Ocean (Fig. l), with  most of the  population (75 to 80%) limited to the Pribilof Islands (NMFS, 1979; Harry  and Hartley, 1981). Other popula- tions occur in the Komandorski Islands and on Tyuleniy (Robben)  Island (Scheffer, 1958). Rookeries recently have become re-established on  Lovushek and Srednev in the Kuril Islands, a part of the former range of the fur seal (Voronov, 1974), and another new  rookery  was  discovered recently  on San Miguel Island off the coast of California (Peterson et ab., 1968). Historical records indicate that fur seals  formerly  bred  on  many of the Kuril Islands but  were extirpated, apparently by human harvest, in the late 19th century (Voronov, 1974). In addition, Murie (1959) sug- gests that fur seals once  bred,  at least intermittently, on Buldir  in the western Aleutian Islands, but  they  have  not been seen breeding there in recent years (R.H. Day, pers. obs., 1975,  1977,  1978). WhilevisitingBogoslofIsland,Alaska(53”56’N, 158°02’W) on 20 July 1980, we discovered a small group of fur seals o,n a boulder  beach on the northwestern side of the island, adjacent to a sandy beach occupied by a rookery of several hundred Steller sea lions (Eumetopias jubarus Schreber). The fur seal  group consisted of one male  with  two females, each with a small (estimated 4-5 kg) pup, and two  lone bulls. The bull accompanying the cows was extremely defensive- and emitted the “whickering” call (Kenyon, w R o s e E N  SAN M I G U E L  - \ FIG. 1. Location of present and historical rookeries of the northern fur seal (adapted from NMFS, 1979). 1960) when we approached the cows and pups. Since copulation  normally occurs a few days after parturition (Barthalomew and Hoel, 1953) our observations suggest that these animals  had bred on Bogoslof. If so, this is the first report offur seals breeding there since this  island rose out of the sea in 1796 (Byrd et al., 1980). There are two previous sightings of northern fur seals on Bbgoslbf Island, both  on the same beach as our finding (CH. Fiscus, pers. comm. 1980). On 23 October 1976 a National  Marine Fisheries Service survey party found a large adult male  hauled out near a group of sea lions. A second NMFS survey on 15 July 1979 saw one adult  male and  one subadult male  among the sea lions. We consider Bogoslof Island a likely site for develop- ment of a fur seal rookery since it  is adjacent to the major pelagic  feeding area also used by fur seals on the Pribilof Islands (Fiscus et al., 1964). This  feeding area is part of  the oceanic  and outer shelf  domains of the Bering Sea which have  been  well  delineated  by recent oceanographic inves- ’ Institute of Marine Science, University of Alaska, Fairbanks, Alaska 99701, U.S.A. NORTHERN FUR SEALS 319 4 72" 168" 4 64" 160" 156" L 172' 168' 464' L ,Fire Island Bogoslof I s land  58' 56' FIG. 2. OceanoeraDhic  domains  and  fur seal rookeries in the southeastern  Bering Sea. Star on inset indicates location of breeding  fur seals sighted on Bogmiofisland. tigations (Iverson et al . ,  1979). In general, the oceanic domain is seaward of the  continental shelf break;  the  outer shelf  domain extends from waters  over  the shelf break shoreward to approximately the 100 meter isobath (Fig. 2). Both the  outer and inner boundaries of the  outer shelf domain are marked  by distinct  oceanographic fronts (Kinder and Schumacher, 1981). This  region of the Bering Sea, and not that  over  the shallower portions of the shelf, supports the highly productive pelagic food web on which the fur seals depend. The outer shelf  and oceanic domains are the feeding habitats for the northern fur seal in this area  (Perez, 1979; Perez and Bigg, 1980), and we  suggest that they are for all fur seal  rookeries. Although strictly comparable oceanographic data  for California and the western North Pacific are not available, all  known  breeding sites of the northern fur seal are close to the shelf  edge  where processes occur that nourish a pelagic system similar to that in the southeastern Bering Sea (Walsh, 1981). We propose that only  islands in or  immediately adjacent to the  outer shelf domain are suitable for  fur  seal  rookeries.  Nonetheless, these seals apparently require more  from  breeding sites than  simply  proximity to  appropriate feeding areas. Many other  islands,  the Aleutians for  example,  are within the outer shelf and oceanic domains but are not  used  by these seals as breeding sites. We suspect  that  the suitability of breeding islands for fur seals is  influenced by the  presence of other  otariids,  spe- cifically sea lions which resemble fur  seals in body  form and social behaviour. Steller  sea lions are  present  at all  of the northern rookeries of the  fur seal during the period of reproduction (Belkin, 1966), albeit on the periphery or on beaches nearby the larger rookeries. The newly estab- lished fur seal colony on San Miguel Island is amid a rookery of California sea lions (Zalophus californianus Les- son) (Peterson et al . ,  1968), and that  on Srednev Island in the Kuril Chain  is in the middle of a very large Steller  sea lion rookery (Voronov, 1974). Of course we realize that coincidence of occurrence of fur  seals with other  otariids on their breeding sites  does not necessarily imply a biologi- cal relationship but it  is a  fact worthy of continued inves- tigation. The  developing fur seal rockery at San Miguel Island is an extreme example of colonization,  since it is  situated  at the  southern limit  of the winter range of the northern fur seal (Wilke and Kenyon, 1954). Peterson et al. (1968) speculated that  the  seals were attracted  to this island by its 320 position  in the path of the cold  California Current and its established rookeries of California sea lions  and northern elephant seals (Mirounga angustirostris Gill). We can  only add the observation that San Miguel  lies at the edge of the narrow shelf off California and is one of the northern Channel Islands influenced by seasonal upwelling of cold oceanic water (R. Lasker, pers. comm. 1980). These conditions also constitute an  outer shelf-oceanic system. Colonizations of Lovushek, Srednev, and  San Miguel islands appear to be examples of successful attempts of expansion of breeding sites by the northern fur seal; presumably other attempts have  been unsuccessful. Al- though  only observed in one  year, fur seals breeding  on Bogoslof  Island  may  well constitute the latest successful attempt to colonize a new area (certainly additional ob- servations are necessary to confirm this). This expansion may  be in response to changing environmental conditions, such as competition  with humans for fish resources or the harvest of these seals on the breeding islands. The expan- sion of a species with a restricted and  well  known  breeding distribution poses several questions about dispersal and behaviour  in seal populations as well as about the ecology of the seas and the impact of human activities on the oceans. ACKNOWLEDGEMENTS This paper is a contribution of the study on Processes and Resources of the  Bering Sea Shelf (PROBES) and the Seagrass Ecosystem Study, both  sponsored by the  National Science Foun- dation  (Grants  DPP-7623340  and OCE-7727050). We  thank F. H. Fay  for his comments on an  early draft of this paper. Contribu- tion No. 448  from the Institute of Marine Science, University of Alaska, Fairbanks. REFERENCES BARTHOLOMEW, G.A. and HOEL, P.G. 1953. Reproductive behav- ior of the Alaska fur seals, Callorhinus ursinus. Journal of Mammalogy BELKIN,  A.N. 1966. The interrelationships of sea lions and fur seals on common breeding rookeries (Translated from Russian). Translation Series No. 767, Fisheries Research Board of Canada. 23 p. 34:417-436. D.S. LLOYD, C.P. McROY and R.H. DAY BYRD, G.V. DIVOKY, G.J. and BAILEY, E.P. 1980. Changes in marine  bird and mammal populations on  an active volcano in Alaska. Murrelet 6150-62. FISCUS, C.H., BAINES, G.A. and WILKE, F. 1964. Pelagic fur seal investigations, Alaska waters, 1962. U.S. Fish and Wildlife Service, Special Scientific Report Fisheries, No. 475. 59 p. HARRY, G.Y. and HARTLEY, J.R. 1981. Northern fur seals in the Bering Sea. In: Hood, D.W. and Calder, J.A. (eds.).  The Eastern Bering Sea  Shelf Oceanography and Resources. Boulder: U.S. De- partment of Commerce, 2. 847-867. IVERSON, R.L. COACHMAN, L.K. COONEY, R.T., ENGLISH, T.S., GOERING, J.J., HUNT, G.L., Jr., MACAULEY, M.C., McROY, C.P., REEBURGH, W.S. and WHITLEDGE, T.E. 1979. Ecological significance of fronts in the southeastern Bering Sea. In: Livingston, R.J.  (ed.). Ecological Processes in Coastal and Marine Systems. New  York:  Plenum Publishing Corporation. 437-466. KENYON, K.W. 1960. Temtorial behaviour and homing  in the Alaska fur seal. Mammalia 24(3):431-444. KINDER, T.H. and SCHUMACHER, J.D. 1981. Circulation over the continental shelf of the Southeastern Bering Sea. In: Hood, D.W. and Calder, J.A. (eds.). The  Eastern Bering Sea Shelf: Oceanography and Resources. Boulder: U.S. Department of Commerce, 1 .  53-75. MURIE, O.J. 1959. Fauna of the Aleutian Islands and Alaska Peninsula. U.S. Fish and Wildlife Service. North American Fauna Series 61: 406 p. NMFS. 1979. Draft Environmental Impact Statement on the Interim Convention on Conservation of North Pacific Fur Seals. National Marine Fisheries Service, Office of Marine  Mammals  and Endangered Species, Washington, D.C. 38 p. PEREZ, M.A. 1979. Preliminary analysis of feeding habits of the north- ern fur seal in the eastern North Pacific and Bering Sea, 1958-1974. In: Preliminary Analysis of Pelagic Fur Seal Data Collected by the Unit- ed States and Canada During 1958-1974.22nd Annual Meeting of the Standing Scientific Committee, North Pacific Fur Seal Commission. -and B E G ,  M.A. 1980. Interim report on the feeding habits of the northern fur seal in the eastern North Pacific Ocean and eastern Bering Sea. In: Further Analysis of Pelagic Fur Seal Data Collected by the United States and Canada during 1958-1974. Part 2. 23rd Annual  Meeting of the Standing Scientific Committee, North Pacific Fur Seal Commission. PETERSON, R.S.,  LE BOEUF, B.J. and DE LONG, R.L. 1968. Fur seals from the Bering Sea breeding in California. Nature 219(5157): SCHEFFER, V.B. 1958. Seals,  Sea Lions and Walruses: A Review of the Pinnipedia. Stanford: Stanford University Press. 179 p. VORONOV, V.G. 1974. Mammals of the Kuril Islands. Leningrad: Science Publishers. (Portion translated by F. H. Fay, University of Alaska, Fairbanks, Alaska.) WALSH, J.J. 1981. Shelf-sea ecosystems. In: Longhurst, A.R. (ed.). Analysis of Marine Ecosystems. London: Academic Press. 159-196. WILKE, F. and KENYON, K.W. 1954. Migration and food of the northern fur seal. Transactions of the 19th North American Wildlife Conference: 430-440. 899-901. 

Discovery of Northern Fur Seals (Callorhinus ursinus) Breeding on Bogoslof Island Southeastern Bering Sea

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Discovery of Northern Fur Seals (Callorhinus ursinus) Breeding on Bogoslof Island Southeastern Bering Sea

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