Abstract. — Depredation of 

 bottomfish on longline catches by 

 killer whales, Orcinus orca, has 

 been documented throughout the 

 Bering Sea. Stations where re- 

 peated interactions with killer 

 whales had been noted were exam- 

 ined during Japan-U.S. cooperative 

 longline research surveys con- 

 ducted from 1980 to 1989. During 

 vessel surveys in 1988, killer 

 whales were shown to depredate 

 Greenland turbot, Reinhardtius 

 hippoglossoides, sablefish. Anoplo- 

 porna fimbria, arrowtooth flounder, 

 Atheresthes stomias, Pacific hali- 

 but, Hippoglossus stenolepis, and 

 searcher, Bathymaster signatus, se- 

 lecting the largest fish available for 

 each species. Depredation rate, 

 based on averages of total catch, 

 was higher than calculated from 

 direct counts of damaged fish. The 

 average annual monetary loss to 

 the survey calculated over a 4-month 

 research season as a result of killer 

 whale predation for the years 1982 

 through 1988 was estimated to 

 range from $2,982 to $34,571 ( from 

 ¥402,500 to ¥4,667,110). 



Killer whale, Orcinus orca, 

 depredation on longline catches 

 of bottomfish in the southeastern 

 Bering Sea and adjacent waters 



Kazunari Yano 



Seikai National Fisheries Research Institute 



Fisheries Agency of Japan 



2-5-20 Higashiyamoto-machi. Shimonoseki 750. Japan 



Marilyn E. Dahlheim 



National Marine Mammal Laboratory, Alaska Fisheries Science Center 



National Marine Fisheries Service, NOAA 



7600 Sand Point Way NE, Seattle, WA 981 1 5-0070 



Manuscript accepted 12 September 1994. 

 Fishery Bulletin 93:355-372 (1995). 



Killer whales, Orcinus orca, are cos- 

 mopolitan in distribution (Leather- 

 wood and Dahlheim, 1978), and re- 

 ports of their interference in fish- 

 ery operations occur worldwide 

 (Sivasubramanium, 1965; Leather- 

 wood et al., 1990; Tasmanian Fish- 

 eries Development Authority 1 ). In 

 Alaska, killer whales depredate 

 longline catches of bottomfish, such 

 as sablefish (also known as black- 

 cod), Anoplopoma fimbria, and 

 Greenland turbot, Reinhardtius 

 hippoglossoides, in the southeast- 

 ern Bering Sea and Prince William 

 Sound, Alaska (Dahlheim 2 ). Infor- 

 mation from sources in the U.S. do- 

 mestic longline fishery in the Bering 

 Sea suggests that killer whale dep- 

 redation occurs on at least 20% of 

 the bottom longline sets (Dahlheim 2 ). 

 In Prince William Sound, an esti- 

 mated 25% of the total catch is lost 

 to killer whales (Matkin 3 ). 



Annual Japan-U.S. cooperative 

 longline research surveys for sable- 

 fish and Pacific cod, Gadus macro- 

 cephalus, resources have occurred 

 in Alaskan waters since 1979. Re- 

 search vessels use similar fishing 

 gear to that used during Japanese 

 commercial bottom longline opera- 

 tions. This study reports on the na- 

 ture and extent of fishery interac- 



tions with killer whales on Japan- 

 U.S. research longline operations in 

 Alaskan waters from 1980 to 1989. 

 The survey area included the east- 

 ern Aleutian Islands, north into the 

 Bering Sea along the continental 

 slope, eastward following the Alaska 

 Peninsula to the Gulf of Alaska, and 

 then south into Southeast Alaska 

 (Fig. 1). Objectives of the study in- 

 clude 1) definition of the areas 

 where fishery interactions occur; 2) 

 estimation of killer whale depreda- 

 tion on longline-caught fish; 3) iden- 



1 Tasmanian Fisheries Development Au- 

 thority. 1981. Assessment of impact of in- 

 terference from Orcinus orca (killer whale) 

 on Tasmanian dropline fishery. Australian 

 National Parks and Wildlife Service, Tas- 

 manian Fisheries Development Authority, 

 23 Old Wharf, Hobart. Tasmania 7000, 

 Australia. Unpubl. manuscr., 35 p. 



2 Dahlheim, M. E. 1988. Killer whale 

 (Orcinus orca) depredation on longline 

 catches of sablefish (Anoplopoma fimbria ) 

 in Alaskan waters. U.S. Dep. Commer., 

 NOAA, Natl. Mar. Fish. Serv., Northwest 

 Alaska Fish. Cent., 7600 Sand Point Way 

 NE, BIN C 15700, Seattle, WA 98 115. Proc. 

 Rep. 88-4, 31 p. 



3 Matkin, C. O. 1986. Killer whale interac- 

 tions with the sablefish longline fishery in 

 Prince William Sound, Alaska, 1985, with 

 comments on the Bering Sea. Rep. to the 

 National Marine Mammal Laboratory, Natl. 

 Mar. Fish. Serv., NOAA, 7600 Sand Point 

 Way N.E., Seattle, WA98115-0070. Unpubl. 

 manuscr. contract 40-HANF-6-0068. 10 p. 



355 



