358 



Fishery Bulletin 93(2). 1995 



Monetary losses incurred during fishing operations 

 were calculated from data for product (kg) and from 

 price per kilogram (yen) of sablefish, Greenland tur- 

 bot, and arrowtooth flounder, contained in the annual 

 survey reports of JAMARC by the following formula: 



Monetary loss (yen and US dollar) = 



(Average product value) x (depredation rate 



[RNT, RNS, REY or REA])/100, 



where average product value is the average of prod- 

 uct values calculated by product per operation and 

 by price per kilogram in each area and each year. 



Results 



Stations with killer whales 



Between 1980 and 1989, killer whales were reported 

 at 25 stations (Fig. 1 ). Eighteen of these stations were 

 in the eastern Bering Sea (B), five stations were near 

 the eastern Aleutian Islands (EA), and one station 

 each was near the Shumagin Islands (SH) and off 

 Kodiak Island (KO). Fishery interactions consistently 

 occurred at several of the sampling locations (Table 

 1). The highest frequency of killer whale interactions 

 was reported for two areas in the Bering Sea: B-I 

 (stations 31, 32, and 33) and B-II (stations 22, 25, 

 26, and 27) (Table 1, Fig. 1). Killer whale group size 

 ranged between 4 and 50 animals during the 1988 

 survey (Table 2). From the 1988 field observations 

 and photographs of killer whales, there appears to 

 be three killer whale groups involved in the Bering 

 Sea fishery interactions (BS1, BS2, and BS3 in Table 

 2; Yano and Dahlheim 14 ). 



Depredation by killer whales 



During the 1988 survey, when killer whales were 

 observed around the vessel, the hooks on the re- 



11 (continued) Fishery Resources Research Center, 3-27 Kioi-cho, 

 Chiyoda-ku, Tokyo 102 Japan, JAMARC Rep. S60/No.l2, 197 

 p. [In Japanese.] 



12 Takeda, Y., and T. Sasaki. 1988. Report on sablefish and Pa- 

 cific cod resource developmental survey, 1986. Japan Marine 

 Fishery Resources Research Center, 3-27 Kioi-cho, Chiyoda-ku, 

 Tokyo 102 Japan, JAMARC Rep. S6I/N0. 12, 179 p. [In Japanese.] 



13 Takeda, Y. 1988. Report on sablefish and Pacific cod resource 

 developmental survey, 1987. Japan Marine Fishery Resources 

 Research Center, 3-27 Kioi-cho, Chiyoda-ku, Tokyo 102 Japan, 

 JAMARC Rep. S62/No.ll, 191 p. [In Japanese.] 



14 Yano, K., and M. E. Dahlheim. Behavior of killer whales, 

 Orcinus orca, during longline fishery interactions in the south- 

 eastern Bering Sea and adjacent waters. Fisheries Science 

 (unpubl. manuscript). 



trieved groundline frequently contained only fish 

 heads, lips, or gills (Fig. 2), providing evidence that 

 killer whales were responsible for depredation of 

 longline-caught fish. Occasionally, whole fish showed 

 extensive rake marks made by killer whale teeth 

 (Figs. 3 and 4). Whales consumed longline catches of 

 sablefish, Greenland turbot, arrowtooth flounder, and 

 Pacific halibut, the latter remaining whole but show- 

 ing extensive rake marks. Two heads of searcher were 

 also noted. Other species offish caught on longlines 

 but not eaten by killer whales included Pacific cod, 

 grenadier, Coryphaenoides acrolepis, rockfish, Se- 

 bastes spp., walleye pollock, Theragra chalcogramma, 

 and shortspine thornyhead, Sebastolobus alascanus. 



Depredation rates 



Killer whale depredation rates calculated by four 

 different methods showed that the rates based on 

 averages of total catch (RE A and REY) were higher 

 than the rates calculated directly from damaged fish 

 (RNT and RNS). Based on our sampling, depreda- 

 tion rates for Greenland turbot were highest, followed 

 by depredation rates for sablefish, arrowtooth floun- 

 der, and Pacific halibut (Table 3). Depredation rates 

 of about 10% or more (based on both RNT and RNS 

 values) were noted for stations 30, 33, 25, 22, and 

 20. The highest RNT and RNS values were found at 

 station 25 for Greenland turbot and sablefish and at 

 station 22 for arrowtooth flounder. Arrowtooth floun- 

 der typically had lower depredation rates than those 

 calculated for Greenland turbot or sablefish. How- 

 ever, a large number of damaged arrowtooth floun- 

 der (15-72 specimens) were present in the catch at 

 stations 30, 17, 20, 22, and 25. 



Annual catch rates (total number of fish caught 

 per hachi) of sablefish, Greenland turbot, and 

 arrowtooth flounder for each station in the EA, B-I, 

 B-II, B-III, and SH areas (Fig. 1) were used to calcu- 

 late depredation rates for all years at each station 

 (REA) and for all stations for each year (REY). 

 Twenty-one stations had fishery interactions involv- 

 ing killer whales during the period 1980-88 (Table 

 4). Depredation rates (REA) calculated from the av- 

 erage fishery catch rates for years with and without 

 killer whale predation showed that the average catch 

 rates of sablefish and Greenland turbot were signifi- 

 cantly lower when killer whales were present than 

 when killer whales were absent (ANOVA, P<0.01). 

 However, for arrowtooth flounder average catch rates 

 were independent of killer whale depredation 

 (ANOVA, P>0.05). In addition average catch of 

 arrowtooth flounder was similar among years regard- 

 less of the presence or absence of whales (Table 4). 

 Depredation rates (REA) calculated from the average 



