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



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Euphausiids 

 Shrimp 

 Other fish 

 Pollock 

 Other 



KAKAKAKA 



<200 201-300 301-400 > 400 

 Predator length group (mm) 



Figure 2.— Percentage by weight of major prey categories in the diet of arrowtooth 

 flounder (A), Atheresthes stomias, and Kamchatka flounder (K), A. evermanni, for dif- 

 ferent length groups of fish collected from the eastern Bering Sea in summer 1983. 



all <5% by weight of the diet of both Atheresthes 

 species. 



The principle diet by weight of Kamchatka 

 flounder in the 301-400 mm size group was com- 

 prised of 55.8% walleye pollock, 13.8% zoarcids, 

 9.4% pleuronectids, 9.5% stichaeids, and 7.9% 

 euphausiids (Table 2, Fig. 3). Walleye pollock also 

 dominated the diet of arrowtooth flounder (77% by 

 weight). The other two main items of arrowtooth 

 flounder were euphausiids (16.2% by weight) and 

 unidentified gadoids (5.7% by weight). Shrimps were 

 not important food for either Atheresthes species of 

 this size; they contributed <1% by weight of the diet. 

 Other less important prey items were ophiuroids and 

 pagurids. Numerically, euphausiids dominated the 

 food for both species (90.7% for Kamchatka 

 flounder, 96.0% for arrowtooth flounder). 



Walleye pollock dominated the food of the two 

 Atheresthes species in the >400 mm size group (Fig. 

 3). It constituted 85.9% and 88.0% by weight of the 

 diet of Kamchatka flounder and arrowtooth 

 flounder, respectively (Table 2). Though euphausiids 

 dominated the food by number (91.5% for Kam- 

 chatka flounder, 97.0% for arrowtooth flounder), 

 they only contributed 4.1% and 6.8% by weight of 

 the diet of Kamchatka flounder and arrowtooth 

 flounder, respectively. In addition to walleye pollock, 



unidentified gadoids comprised 8.2% and pleuronec- 

 tids comprised 1.8% by weight of the diet of Kam- 

 chatka flounder. Zoarcids comprised 5.1% by weight 

 of the diet of arrowtooth flounder. Shrimps played 

 a less important role in the food of both Atheresthes 

 species (<1% by weight). 



Diet Comparison Among Size Groups 



There was not much difference in diets among size 

 groups in the proportion by weight of the prey 

 categories such as euphausiids and fish (Fig. 2). 

 However, shrimps disappeared from the diets of 

 flounders in the two larger size groups. The number 

 of different species in the diet also changes with size. 

 The <200 mm size group of flounders consumed 

 about 11 or 12 different prey categories while the 

 >400 mm size groups consumed only 3 or 4 differ- 

 ent prey types (see Table 2). 



Even though the proportion by weight of fish in 

 the diet remained fairly constant over flounder size 

 groups, the size of individual fish consumed did 

 change with flounder length. Figure 4 shows the fre- 

 quency distribution of fish prey lengths found in the 

 stomachs of different size A. evermanni. Most of the 

 prey fish were age-0 juvenile pollock (<100 mm) for 

 the two smaller size groups and age-1 juvenile 



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