Wilson et al.: Geographic variation among age-0 Theragra chalcogramma 



213 



able. Copepods dominated the 

 catches in Chiniak Bay and over 

 the shelf, whereas larval crabs 

 were most prevalent in the Ugak 

 and Kiliuda samples (Table 5B). 

 In terms of overall abundance, 

 mean prey densities were lowest 

 among samples collected from the 

 shelf and highest for the Chiniak 

 Bay samples. 



Discussion 



The presence of age-0 pollock in 

 bays and over the inner shelf, but 

 not over the outer shelf, indicates 

 that the principal pollock nurs- 

 ery off east Kodiak Island during 

 autumn is relatively close to shore. 

 Earlier studies of age-0 pollock in 

 the western GOA focused on near- 

 shore areas (Smith et al., 1984; 

 Wilson, 2000) and did not docu- 

 ment the absence of age-0 pollock 

 over the outer shelf. Our results 



point to prey resource as a likely explanation for the 

 observed distribution of and differences among age-0 

 walleye pollock. 



Seasonal declines in zooplankton density underscore 

 the importance of nearshore areas as pollock nurseries. 

 Rogers et al. 1 and Kendall et al. 2 observed an order-of- 

 magnitude autumnal decline in prey 3 density off Kodiak 

 Island during 1977-79 (Fig. 8). This decline was accom- 

 panied by a shoreward shift in the region of highest eu- 



2 Kendall, A. W., Jr., J. R. Dunn, R. J. Wolotira Jr., J. H. 

 Bowerman Jr., D. B. Dey, A. C. Matarese, and J. E. Munk. 

 1980. Zooplankton, including ichthyoplankton and deca- 

 pod larvae, of the Kodiak shelf. NOAA NWAFC proc. rep. 

 80-8, 393 p. Alaska Fishery Science Center, Seattle, WA. 



3 All invertebrate zooplankters are considered potential age-0 

 pollock prey except cnidarians, ctenophores, siphonophores, 

 and larval shrimps and crabs. Shrimp and crab were omitted 

 from Figure 8 because density estimates were not available 

 separately for the shelf and slope regions. 



