Water masses defined hy zooplankton 



Theragra Chalcogramma 



180° 



1750 LONGITUDE 170° 



165° 



Fig. 4. 



Dislributionof Anadyr and Bering Shelf water masses. Water masses 

 were delineated by the species of /.ooplankton present in samples from 

 94 stations. Larvae of T chalcogramma occur where shelf waters 

 overlie oceanic waters. 



The larger size range of larvae arc approximately 35 days 

 old. If we add the incubation time for eggs of 14 days, these 

 larvae could have been transported 740 km, placing them in our 

 study area. The original spawning stock for these fish could be 

 the continental slope area northwest of the Pribilof Islands, 

 where spawning takes place as late as October (Hinckley, 

 1987). 



Two additional gadids, B. saida and E. gracilis, occurred 

 in the Chirikov basin and Chukchi Sea where BSW overlay 

 ASW, associated with chlorophyll values of 200-600 mg/m-. 

 Two size modes were present, newly hatched larvae (5 mm SL) 

 and larger larvae (20 mm SL). Both species occur within the 

 known spawning areas and the area of adult distributions 

 (NOAA, 1987). 



The flatfishes area represented principally by two species. 

 Hippoglossoides elassodon concentrate at the eastern edge of 

 the Gulf of Anadyr where BSW overiay ASW associated with 

 relatively low integrated chlorophyll values (1 00 mg/m-). The 

 samples are dominated by new hatched larvae (5 mm SL) and 

 a few larger larvae ( 1 5 mm SL). The newly hatched larvae are 



5 10 15 20 



LENGTH (mm Standard length) 



Fig. 5. Size frequency histogram of T. chalcogramnui larvae. Two size 

 groups occur, new hatched larvae (4-7 mm SL) and older larvae 

 (20-25 mm SL). 



present north of reported spawning grounds and much later in 

 the season than major spawning ( winter-spring)(NOAA, 1987). 

 Again either larval transport into the area in Anadyr waters 

 and/or a later more northerly spawning population can account 

 for the presence of these larvae . 



Limanda sp. is probably the yellowfin sole, L. aspera. 

 Positive identification could not be made due to the occurrence 

 of L. prohoscidea in the study area, for which there is not larval 

 description. Limanda sp. occurs in the Chukchi Sea in middle 

 shelf water associated with relatively low chlorophyll values. 

 Larvae range from 5 to 15 mm SL and occur in known 

 spawning areas and during the spawning season. 



Conclusions 



7. Larval tlsh susceptible to capture in a 1-m, bridled 

 plankton net were primarily commercially important species. 

 Walleye pollock (40% of the total larval fish) and flathead sole 

 (38% of the total larval fish) were dominant species. This study 

 is a preliminary evaluation of the species composition and 

 distribution of larval fishes. The number of larval fish 

 underestimates the abundance due to patchy distributions 

 and the potential ability of larval fish to avoid the net 

 we used. 



2. The presence of larvae in the study area could be 

 accounted for in most cases by known spawning stocks of the 

 species in the area or by advective transport from known 

 spawning regions. However, for 7". chalcogramma and 

 H. elassodon, some of the newly hatched larvae were far north 

 of known spawning areas, suggesting the possibility of as yet 

 unknown spawning stocks. 



3. The results indicate a distribution of larval fishes that 

 warrants further investigation with the appropriate gear, 

 sampling both larval and adult populations. We plan to 

 investigate the possibility of a northern population of spawning 

 walleye pollock in the area north of St. Lawrence Island. 



197 



