DISTRIBUTION OF MARINE MAMMALS IN THE COASTAL ZONE OF THE BERING SEA DURING SUMMER AND AUTUMN by Kathryn J. Frost, Lloyd F. Lowry, and John J. Burns Alaska Department of Fish and Game 1300 College Road Fairbanks, Alaska 99701 Assisted by Susan Hills and Kathleen Pearse Final Report Outer Continental Shelf Environmental Assessment Program Research Unit 613, Contract Number NA 81 RAC 000 50 1 September 1982 365 TABLE OF CONTENTS Page I. Summary •. 373 I I. Introduction . ·" . 374 III. Current State of Knowledge . 375 IV. Study Area 387 V. Methods 388 VI. Results 395 A. North Aleutian Basin . ..... 395 B. St. George Basin .......•. 445 C. St. Matthew-Hall Basin ..... 452 D. Norton Basin . ....•. 471 VII. Discussion ..... 499 A. Steller Sea Lion 499 B. Harbor Seal .. 503 C. Spotted Seal . 506 D. Pacific Walrus . 507 E. Belukha Whale . 511 F. Harbor Porpoise 513 G. Killer Whale 513 H. Minke Whale 516 I. Gray Whale . 516 J. Sea Otter 519 VII I. Conclusions 521 A. Adequacy of Sighting Data . 521 B. Importance of Coastal Regions to Marine Mammals . 522 C. Potential Effects of OCS Activities . 524 IX. Needs for Further Study 526 x. Literature Cited .... 527 Appendix I. Geographical Coordinates of Locations Referred to in the Text . • . ........ 539 Appendix II. Source Names Index ... 551 367 LIST OF FIGURES Figure Page 1. Map of the study area showing Outer Continental Shelf planning areas ......•.....•. 389 2. Map of the North Aleutian Basin planning area showing subdivisions used in data compilation 396 3. Map of the North Aleutian Basin, region NAB 1 397 4. Map of the North Aleutian Basin, region NAB 2 412 5. Map of the North Aleutian Basin, region NAB 3 420 6. Map of the North Aleutian Basin, region NAB 4 426 7. Map of the St. George Basin, region SGB 1 446 8. Map of the St. Matthew-Hall Basin planning area showing subdivisions used in data compilation 453 9. Map of the St. Matthew-Hall Basin, region SMH 2 456 10. Map of the St. Matthew-Hall Basin, region SMH 4 464 11. Map of the Norton Basin planning area showing subdivisions used in data compilation .•.. 472 12. Map of the Norton Basin, region NB 1 473 13. Map of the Norton Basin, region NB 2 478 14. Map of the Norton Basin, regions NB 3, 5, and 6 484 15. Map of the Norton Basin, region NB 4 . 487 16. Map of the eastern Bering Sea showing locations where Steller sea lion haulouts have been recorded 500 17. Map of the eastern Bering Sea showing major haulouts used by harbor and spotted seals 505 18. Map of the eastern Bering Sea showing major known haulouts of walruses ....•..•• 508 19. Map of the eastern Bering Sea showing sightings of belukha whales in the coastal zone •••.• 512 368 Figure Page 20. Map of the eastern Bering Sea showing sightings of harbor porpoises in the coastal zone .... 514 21. Map of the eastern Bering Sea showing areas where the presence of killer whales has been reported 515 22. Map of the eastern Bering Sea showing sightings of minke whales in the coastal zone .....• 517 23. Map of the eastern Bering Sea showing locations where gray whales have been sighted ..... 518 24. Distribution of sea otters north of the Alaska Peninsula and Unimak Island in 1970 and 1976 . 520 369 LIST OF TABLES Table Page 1. Geographical subdivisions of the Bering Sea study area 390 2. Information sources consulted in addition to published literature . 392 3. Sightings of coastal marine mammals in the North Aleutian Basin, region NAB 1 . 398 4. Sightings of coastal marine mammals in the North Aleutian Basin, region NAB 2 . 413 5. Sightings of coastal marine mammals in the North Aleutian Basin, region NAB 3 . 421 6. Sightings of coastal marine mammals in the North Aleutian Basin, region NAB 4 . 427 7. Sightings of coastal marine mammals in the Pribilof Islands, St. George Basin, region SGB 1 . 447 8. Sightings of coastal marine mammals in the St. Matthew-Hall Basin, region SMH 1 454 9. Sightings of coastal marine mammals around Nunivak Island in the St. Matthew-Hall Basin, region SMH 2 . 457 10. Sightings of coastal marine mammals in the St. Matthew-Hall Basin, region SMH 3 460 11. Sightings of coastal marine mammals on St. Matthew, Hall, and Pinnacle islands in the St. Matthew-Hall Basin, region SMH 4 .•.....•.•.....• 465 12. Sightings of coastal marine mammals in the Norton Basin, region NB 1 . 474 13. Sightings of coastal marine mammals in the Norton Basin, region NB 2 . 479 14. Sightings of coastal marine mammals in the Norton Basin, region NB 2 . 485 15. Sightings of coastal marine mammals around St. Lawrence Island and the Punuk Islands in the Norton Basin, region NB 4 . 488 370 Table Page 16. Sightings of coastal marine mammals on King Island in the Norton Basin, region NB 5 ....... 493 17. Sightings of coastal marine mammals around the Diomede Islands in the Norton Basin, region NB 6 494 18. Maximum recorded numbers of sea lions hauling out on Unimak and Amak islands, Sea Lion Rocks, and the Pribilof Islan~s from 1956 through 1982 ... 501 19. Maximum recorded numbers of sea lions hauling out in northern Bristol Bay from 1957 through 1982 . 502 20. Summary of information on major walrus hauling areas in the eastern Bering Sea ........ 509 21. Maximum recorded numbers of pinnipeds hauled out on major offshore islands in the eastern Bering Sea, based on recent sightings ............. 523 371 I • Summary A study was conducted with the objectives of compiling al I availa­ ble sightings of marine mammals in the coastal zone of the eastern Bering Sea during summer and autumn and evaluating the importance of coastal areas to the various species. Specific attention was given to identification of terrestrial hauling areas used by pinnipeds, and bays, lagoons, and estuaries uti I ized by cetaceans. The study area included the mainland coast, as wel I as major offshore islands, but did not include the Aleutian Islands. Based on available sightings, it was possible to identify In general terms the areas of greatest importance to marine mammals, as wel I as to examine some aspects of seasonal distribution and abundance in specific areas. Although marine mammals inhabit the entire coastal zone of the eastern Bering Sea during summer and autumn, their distri­ bution is far from uniform. Sea otters occur principally along the southwestern portion of the Alaska Peninsula, with a few animals on the Pribilof Islands. Steller sea I ions haul out on most offshore islands and along rocky portions of the mainland coast in northwestern Bristol Bay. The only presently active breeding rookeries are at Sea Lion Rocks near Amak Island and Walrus Island in the Pribilof Islands. Major haulouts for walruses are at Cape Seniavin and Round Island in Bristol Bay, and at the Punuk Islands, St. Lawrence Island, King Island, and Big Diomede Island in the northern Bering Sea. Most Bering Sea harbor seals haul out at several locations along the north side of the Alaska Peninsula. Harbor seals and spotted seals mix in northern Bristol Bay and portions of the Kuskokwim Delta. Major haulouts in those regions occur at Nanvak Bay and in Kuskokwim Bay. Spotted seal hauling areas occur on St. Matthew Island, Hal I Island, St. Lawrence Island, Golovnin Bay, and Port Clarence. Gray whales migrate through the entire coastal zone of Bristol Bay, pass along the south and west sides of Nunivak Island, and occur commonly near St. Lawrence Island. Major concentration areas for belukhas occur in Kvichak, Nushagak, Golovnin, and Norton bays and off the mouths of the Yukon River. Harbor porpoises are occasionally seen along the entire mainland coast, with several recent records from Norton Sound. Minke whale sightings have occurred primarily off the Alaska Peninsula, Nunivak Island, and Golovnin Bay. We located only one sighting of a killer whale in the coastal zone. Available data indicate substantial fluctuations in numbers of animals at particular locations but are not adequate to measure those fluctuations or explain their causes. We suggest that OCSEAP initiate studies on representative species and areas in order that the effects of OCS activities on marine mammals in the coastal zone can be rigorously evaluated. 373 I I. Introduct Ion Approximately 26 species of marine mammals are known to occur with some regularity In the Bering Sea. Included are eight species of pinnlpeds, eight mystlcete cetaceans, eight odontocete cetaceans, and two carnivores (Fay 1974, Lowry et al. 1982b). While a number of species such as several of the Ice-associated pinnipeds and the oceanic cetaceans are seldom It ever seen near shore, several others regularly utll lze coastal habitats. During summer and autumn when the coastal zone is ice tree, 10 species may be common components of the nearshore fauna. They are: SteI ler sea 11 on, Eumetop i as jubatus Harbor seal, Phoca vitul ina richardsi Spotted seal, Phoca largha Walrus, Odobenus rosmarus divergens Belukha whale, Delphinapterus leucas Harbor porpoise, Phocoena phocoena Kl Iler whale, Orcinus ~ Minke whale, Balaenoptera acutorostrata Gray whale, Eschrichtius robustus Sea otter, Enhydra lutris Fur seals (Cal lorhinus ursinus), which haul out almost exclusively on the Pribi lot Islands, were not included in this study. While in the coastal zone, al I of the above species forage on the abundant food resources available in nearshore waters. In addition, seals, sea lions, walruses, and sometimes sea otters commonly haul out at specific coastal locations. For walruses, coastal haulouts appear to be important principally as a place to rest between feeding forays, while harbor seals and sea I ions give birth, care tor, and nurture their young, and molt on land.