Zimmermann and Goddard Biology and distribution of Atheresthes stomias and A evermanni 



365 



(>40 cm FL) were caught near the edge of the Bering 

 Sea shelf, in the Bering Sea slope area, and through- 

 out the Aleutian Islands regions. 



There was a difference in the temperature regimes 

 of the Aleutian Islands and eastern Bering Sea re- 

 gions. In waters off the Aleutian Islands, where col- 

 lection of length data combined with bottom tempera- 

 ture data was scant (ft = 18), there was a significant, 

 negative relationship between length and bottom 

 temperature (df=16, F=13.5, P=0.002, i? 2 =0.46): 

 smaller fish were present in the shallowest and 

 warmest water ( -5° to 6°C) whereas larger fish were 

 found in deeper, cooler water, approaching 4°C. On 

 the Bering Sea shelf and slope, there was a more 

 complex relationship between fish size and bottom 

 temperature, described by a large number (;? = 116) 

 of observations. As fish size increased with depth, 

 the bottom temperature dropped from 4.1"C (<30 cm 

 FL, n=10) to 3.3°C (from <30 to <40 cm FL, »=43), 

 and to 2.4°C (>40 cm FL, re=12) near the shelf edge, 

 though the largest fish were located where the bot- 

 tom temperature increased (3.9°C, n=51) in the slope 

 area. 



For Kamchatka flounder, the group of smaller size 

 fish was eliminated from analysis because it was rep- 

 resented by only five hauls, and for only two of those 

 hauls had bottom temperatures been recorded. The 

 groups of medium- and large-size Kamchatka floun- 

 der had geographic distributions similar to groups 

 of comparable-size arrowtooth flounder. The medium- 

 size (from <30 to <40 cm FL) Kamchatka flounder 

 were found on the Bering Sea shelf generally between 

 the 100 m and 200 m isobaths; however, they did not 

 extend along the Alaska Peninsula nor near the east- 



ern Aleutian Islands as did arrowtooth flounder. The 

 group of large-size Kamchatka flounder (>40 cm FL) 

 was found along the edge of the Bering Sea shelf, 

 the Bering Sea slope, and throughout waters off the 

 Aleutian Island chain, similar in geographic range to 

 arrowtooth flounder. However, they were absent from 

 the eastern islands. The bottom temperature data for 

 the Kamchatka flounder was similar to that of the 

 arrowtooth flounder, except that there were fewer data. 



Arrowtooth flounder catches typically had a high 

 percentage of females, whereas the Kamchatka floun- 

 der catches taken from the same trawl hauls gener- 

 ally had an equal sex ratio (our observations). In the 

 eastern Bering Sea, the arrowtooth flounder popu- 

 lation had a greater percentage of females (68.6%) 

 than did the Kamchatka flounder population (55.9% 

 female) (Table 2). Arrowtooth flounder also had a 

 greater percentage of females than did Hippoglos- 

 soides spp. (51.7% female), Alaska plaice (Pleuro- 

 nectes quadrituberculatus , 42.3% female), rock sole 

 (P. bilineatus, 48.9% female) and yellowfin sole (P. 

 asper, 54.2% female). 



In the Aleutian Islands, arrowtooth flounder also 

 had a higher percentage of females (59.6% female) 

 than did Kamchatka flounder ( 47.5% female ) and rock 

 sole (52.6% female), the only species encountered in 

 sufficient numbers in trawl hauls for comparison. 



Plotting female percentage values of arrowtooth 

 flounder geographically did not indicate any large 

 areas where the percentage of females was low. Nor 

 did it indicate areas where the population had a low 

 percentage of females but was either undersampled 

 or outside of the sampled area. The percentage of 

 females was not significantly related to depth 



