YANG and LIVINGSTON: FOOD HABITS AND DIET OF TWO CONGENERIC SPECIES 



Table 1 .—Station information and number of stomachs collected at each station of arrowtooth 

 flounder (ATF) and Kamchatka flounder (KF) in the eastern Bering Sea for the summer 1983. 



'Stomachs containing food, number of empties in parentheses. 



(Cailliet and Barry 1979; Linton et al. 1981), 

 Schoener's (1970) index was chosen because it was 

 found to measure overlap accurately over most of 

 the range of potential overlap (Linton et al. 1981). 

 Schoener's index, Cxy, is calculated as 



Cxy = 1.0 - 0.5(I|p^ - V J) 



where p x t and p yi are the estimated proportions by 

 weight of prey i in the diets of species x and y, 

 respectively (the percentage by weight of prey items 

 in Table 2). The index ranges from which indi- 

 cates no dietary overlap to a maximum overlap of 

 1 when all prey items are found in equal propor- 

 tions. 



communis, were the dominant shrimp consumed. 

 Walleye pollock constituted the highest proportion 

 of the diet for all size groups of flounder, ranging 

 from 56% by weight of the diet for Kamchatka 

 flounders 301-400 mm long to about 88% by weight 

 for arrowtooth flounders >400 mm long. Miscella- 

 neous food items consumed included polychaetes, 

 copepods, cumaceans, hippolytid shrimps, ophi- 

 uroids, and various fish species. 



Mean stomach content weight of those stomachs 

 with food was similar between arrowtooth flounder 

 and Kamchatka flounder for all but the largest size 

 group. The mean stomach content weight ranged 

 from about 1.4 g for the small flounders to over 20 

 g for the largest size group. 



RESULTS 



General Feeding Trends 



A total of 348 stomachs were analyzed; 87 

 stomachs (25%) were empty. Table 2 shows the per- 

 centages by weight of all prey items found in the 

 stomachs of both flounder species by size group. In 

 general, both species consumed the same prey 

 species or groups: euphausiids, pandalid and 

 crangonid shrimps, and walleye pollock (Fig. 2). 

 Thysanoessa inermis and T. raschii were the domi- 

 nant euphausiids consumed. Some pandalid shrimps 

 were eaten by smaller (<301 mm) flounders of both 

 species, but crangonid shrimps, mainly Crangon 



Diet Comparisons Within Size Groups 



The principle diet of both Atheresthes species in 

 the <200 mm size group was comprised of walleye 

 pollock, euphausiids, and shrimps (Fig. 3). Walleye 

 pollock comprised 58% and 65.5% by weight of the 

 diet of Kamchatka flounder and arrowtooth 

 flounder, respectively. Euphausiids comprised the 

 highest percentage by numbers of the diet of both 

 species, 53% for Kamchatka flounder and 69.4% for 

 arrowtooth flounder. Shrimps, including Crangon 

 communis, Pandalus goniurus, Pandalus tridens, 

 and Eualus avinus, constituted 17.1% and 7.2% by 

 weight of the diet of Kamchatka flounder and arrow- 

 tooth flounder, respectively. Other less important 



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