FOOD HABITS AND DAILY RATION OF GREENLAND HALIBUT, 



REINHARDTIUS HIPPOGLOSSOIDES, IN 



THE EASTERN BERING SEA 



M. S. Yang and P. A. Livingston' 



ABSTRACT 



This study shows that diet of Greenland halibut varies mainly by depth and size, and that size of prey 

 fish increases as the Greenland halibut increases in size. A total of 1,333 Greenland halibut (or turbot), 

 Reinhardtius hippoglossoid.es, stomachs were collected in the eastern Bering Sea from May 1983 to 

 November 1985 and analyzed. Stomach content data were divided into four groups based on sample loca- 

 tion (depth). Using length of the sample animals within each depth group, data were further divided 

 into five size groups. Walleye pollock, Theragra chalcogramma, was the most important prey (58% by 

 weight of the total stomach content). Squids (mainly Berryteuthis sp.) were the second most (20% by 

 weight) important food of Greenland halibut. Zoarcids and some deep-water fishes (e.g., bathylagids, 

 myctophids, macrourids) were also important food for Greenland halibut 30-69 cm long. Euphausiids 

 were only important as food (64% by weight) of the fish <20 cm collected in the continental shelf <200 

 m deep. Fishes >70 cm fed almost exclusively on fish in all depth areas. 



Variation in mean stomach content weight throughout the day was used to determine the diel feeding 

 pattern; from this it appears that Greenland halibut is a continuous feeder. Daily rations (% of body 

 weight per day) of Greenland halibut were calculated using an exponential gastric evacuation rate model. 

 Fish >70 cm had a higher daily ration value (1.17% of body weight per day) than did those of the two 

 smaller size groups (0.66 and 0.64% of body weight per day for 30-49 and 50-69 cm size groups, 

 respectively). 



Greenland halibut (or turbot), Reinhardtius hippo- 

 glossoides, is an amphiboreal fish, occurring in both 

 the North Atlantic and the North Pacific, but not 

 in the intervening Arctic Ocean (Hubbs and Wili- 

 movsky 1964). Within this range, the species has 

 been most extensively studied in the Atlantic Ocean. 

 In the Pacific Ocean, Greenland halibut has been 

 found from Baja California (Schmidt 1934), Oregon 

 (Niska and Magill 1967), and Vancouver B.C. (West- 

 rheim and Pletcher 1966), through the Bering and 

 Okhotsk Seas (Shmidt 1950), to Honshu Island, 

 Japan (Hart 1973), but the center of abundance is 

 in the eastern Bering Sea area. 



Data of the resource assessment surveys (from 

 1979 to 1985) in the eastern Bering Sea performed 

 by the Northwest and Alaska Fisheries Center 

 (NWAFC), National Marine Fisheries Service 

 (NMFS), show that Greenland halibut ranked 

 between 5th and 12th place in terms of relative 

 abundance (kg/ha) among the groundfish species; 



however, it is the most abundant species in continen- 

 tal slope areas (Bakkala 1986^). 



These assessments suggest that Greenland halibut 

 is a key member of the eastern Bering Sea ecosys- 

 tem. The importance of this species in predator-prey 

 relationships of this ecosystem is poorly understood 

 since little is known about its food habits and food 

 consumption rate. Food habits of Greenland halibut 

 in the North Atlantic have been studied by Bower- 

 ing and Lilly (1985) and Haug and Gulliksen (1982). 

 In the eastern Bering Sea, Mikawa (1963), Mito 

 (1974). Smith et al. (1978), and Livingston et al. 

 (1986) reported stomach contents analysis of the 

 Greenland halibut, but the sample sizes in these 

 studies were small and the analyses were limited. 

 The objective of this study is to provide a descrip- 

 tion of the food habits of Greenland halibut in the 

 eastern Bering Sea, including diel, spatial, and 

 seasonal variations in stomach contents; influence 

 of predator size; and daily ration. 



'Northwest and Alaska Fisheries Center. National Marine Fish- 

 eries Service. NOAA. 7600 Sand Point Way N.E., BIN C15700. 

 Building 4, Seattle. WA 98115. 



^Bakkala, R. G. 1986. Greenland turbot— biological report. 

 Unpubl. manuscr., 21 p. Northwest and Alaska Fisheries Center, 

 National Marine Fisheries Service, NOAA. 7600 Sand Point Way 

 N.E.. Seattle, WA 98115. 



Manuscript accepted June 1988. 



FISHERY BULLETIN: VOL. 86. NO. 4. 1988. 



675 



