Yano and Dahlheim: Depredation of bottomfish on longline catches by Orcinus orca 



365 



partially consumed fish (Fig. 9C) was significantly 

 larger than that reported from all areas fished (Fig. 

 9A; £=7.71, P<0.05) and for the stations fished where 

 killer whales were present (Fig. 9B; t = 10.99, P<0.05). 

 There was a bimodal length-frequency distribution 

 for Greenland turbot (Fig. 10, A-C). Average length 

 of Greenland turbot was 744.3 mm TL for all areas 

 fished, 730.8 mm TL for the stations fished where 

 depredation occurred, and 756.1 mm TL for the par- 

 tially consumed fish. Significant differences were 

 found between average lengths of damaged fish and 

 undamaged fish for all stations with killer whale dep- 

 redation (£=2.03, P<0.05 ). However, no significant dif- 

 ferences were found between average lengths of dam- 

 aged fish and undamaged fish for all areas fished 

 U=1.08,P>0.05). The average length of damaged fish 

 was significantly larger than that of undamaged fish 

 at stations with killer whale depredation (£=2.03, 

 P<0.05) but the total average length was about equal 

 to that for all areas fished. 



Monetary loss 



For the years 1982-88, data were collected on the 

 product yield of each area and operation, unit price 

 per kilogram (commercial price when landed), and 

 product price per operation for sablefish, Greenland 

 turbot, and arrowtooth flounder (Table 7). The aver- 

 age monetary loss in the total catch per operation 

 (using 160 hachi per operation) was estimated to 

 range from ¥96,853.7 ($717.40 [U.S. dollars] @Y135 

 calculated from RNT) to ¥790,934.2 ($5,858.80 cal- 



culated from REAKTable 8). The average overall loss 

 incurred for all years at all stations (Table 9) as a 

 result of killer whale depredation ranged from 

 ¥402,499.6 to ¥4,667,109.6 (from $29,181.50 to 

 $34,571.20). The total product value of the 4-month 

 survey for each year (D in Table 9) ranged from 

 ¥98,812,086.0 to ¥283,932,240.0 (from $731,941.40 

 to $2,103,201.80) and the product values per opera- 

 tion (yearly total product value/number of stations 

 per each survey, Pin Table 9 ) ranged from ¥950,116.2 

 to ¥2,629.002.2 (from $7,037.90 to $19,474.10; Table 

 9). The yearly loss was 0.21 to 2.96% (G in Table 9) 

 of the total product value in survey and 3.80 to 

 34.22% (H in Table 9) of the product value per sta- 

 tion (per operation). These values suggest that the 

 rate of yearly overall loss is not large (less than 3%) in 

 total product (survey area is extensive, ranging from 

 the Aleutian Islands to Southeast Alaska in Figure 1 ), 



