I'lSllKKV HII.LKTIN: VOL. 8t;. NO. 4 



ions'*). Because of the small differences in temper- 

 atures between different seasons (e.g., 2.90°C, 

 2.47°C, and 2.93°C were the average temperatures 

 for spring, summer, and autumn at locations where 

 fish 30-49 cm were collected), and the lack of sam- 

 ples for fish <30 cm, daily rations were calculated 

 for three size groups (30-49 cm, 50-69 cm, and >70 

 cm) with all seasons combined. Temperatures used 

 for each of the three size-groups were calculated by 

 matching the haul locations of each size group in our 

 study with the long-term monthly mean bottom 

 temperature at those positions and calculating the 

 average bottom temperature. 



RESULTS 



General Description of Diet 



Stomachs from 1,333 Greenland halibut were 

 analyzed; of these, 610 stomachs (46%) were empty. 

 The size of the Greenland halibut ranged from 9 to 

 99 cm (fork length) with a mean of 56 cm. The sam- 

 pling depth ranged from 62 to 891 m with most of 

 the samples (55%) collected from the area 400-599 

 m deep. 



Prey consumed included gastropods, cephalopods, 

 crustaceans, ophiuroids, and fish (Table 1). Twelve 

 families offish and at least 14 different fish species 

 were represented in the stomach contents. Fish 

 dominated the contents in terms of frequency of oc- 

 currence, number, and weight; walleye pollock was 

 the most important fish species consumed with 

 respect to all three measures of prey importance. 

 Three genera of squid were consumed (mainly 

 Berryteuthis sp.) and were the second most impor- 

 tant prey. The importance of the various prey 

 species or groups (e.g., gadids, squids) changes with 

 bottom depth and Greenland halibut size. Those 

 changes will be discussed in the following sections. 



Spatial and Size Differences 



Depth 1 (<200 m) 



Gadids constituted more than 87% by weight of 

 the stomach contents of all but the smallest (<20 cm) 

 size group (Fig. 2A). Euphausiids comprised 64% 

 by weight (54% by number) of the diet of Greenland 

 halibut <20 cm long. In size group 20-29 cm, the 



■•Ingraham, W. J. 1983. Temperature anomalies in the eastern 

 Bering Sea 1953-82. NWAFC Processed Rep. 83-21, 348 p. 

 Northwest and Alastca Fisheries Center, National Marine Fisheries 

 Service, NOAA, 7600 Sand Point Way N.E., Seattle, WA 98115. 



percentage by number of euphausiids was still high 

 (52%), but the percentage by weight decreased 

 dramatically to only 2%. Gadids were the dominant 

 prey for size groups larger than 30 cm in Depth 1 

 in terms of percent of frequency of occurrence, per- 

 cent of total stomach contents weight, and the 

 percent of prey number. Cephalopods, clupeids, 

 osmerids, stichaeids, myctophids, and macrourids 

 were not important food items at this depth. 



Depth 2 (200-399 m) 



No Greenland halibut smaller than 30 cm were col- 

 lected at this depth range. Cephalopods, in terms 

 of the three diet measures shown in Figure 2B, were 

 the dominant food items found in the size groups 

 30-49 cm and 50-69 cm. On the other hand, gadids 

 were the dominant prey in size group >70 cm (Fig. 

 2B). When all sizes were combined, the cephalopods 

 were more important than gadids (Fig. 2B, lower 

 right); however, when the size groups were sepa- 

 rated (Fig. 2B), the different contribution of gadids 

 and cephalopods to different size groups is very clear 

 (cephalopods are most important for fish <70 cm and 

 gadids are important for fish ^70 cm). Miscellaneous 

 prey fishes found in the entire Depth 2 group 

 included zoarcids, bathylagids, myctophids, and 

 pleuronectids. 



Depth 3 (400-599 m) 



No stomachs of Greenland halibut smaller than 30 

 cm were collected in this depth range (Fig. 2C). For 

 Greenland halibut 30-49 cm long, zoarcids (38.6%) 

 were the most important prey item in terms of 

 percentage by weight of the stomach contents, 

 followed by cephalopods (30.7%) and gadids (17%). 

 In terms of percent of prey number, cephalopods 

 comprised 39% of the total prey in this size group, 

 followed by gadids (22%), bathylagids (17.3%), and 

 zoarcids (8.7%). For the size group 50-69 cm, 

 cephalopods, gadids, and zoarcids comprised 61, 21, 

 and 12% by weight of the stomach contents, respec- 

 tively. Cephalopods also comprised the highest 

 percentage (35%) by the number in this size group. 

 Gadids were the dominant prey of large Greenland 

 halibut (>70 cm). They comprised 87% by weight, 

 69% by number, and 82% by frequency of occur- 

 rence of the stomach contents of this size group (Fig. 

 2C). Other prey fishes found in the Depth 3 group 

 included stichaeids, myctophids, cottids, macroiu^ids, 

 cyclopterids, and pleuronectids. For the Depth 3 

 group (Fig. 2C, lower right), gadids were the domi- 



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