CONTRASTING YEARS OF PREY LEVELS, FEEDING CONDITIONS AND MORTALITY OFLARVAL WALLEYE POLLOCK THERAGRA-CHALCOGRAMMA IN THE WESTERN GULF OF ALASKA

Walleye pollock in Shelikof Strait, Gulf of Alaska, spawn in an area w ith strong interannual differences in the oceanic environment. Feeding conditions and mortality of walleye pollock larvae in Shelikof Strait were compared in 2 consecutive years of markedly contrasting oceanogr aphic conditions. In 1990, winds were relatively calm, and a large edd y was formed in the lower portion of the strait; walleye pollock larva e were found concentrated in this eddy feature. In 1991, winds were ve ry strong and sea surface temperatures were anomalously cold. Flow thr ough the Shelikof region was strong in that year, and larvae were spar se. In 1990, copepod naupliar abundance was high throughout the study area. There were no geographic differences in feeding intensity of lar vae, RNA content or larval growth. In 1991 the major differences occur red between inshore and offshore stations. Comparing conditions in 199 0 and 1991, naupliar abundance, larval feeding intensity, RNA content and length-at-age were all low in the stormy conditions of 1991. In 19 91 estimated mortality was significantly higher than that measured in 1990, although part of the loss could have been due to strong advectio n out of the area. Survival of expatriated larvae is discussed in Ligh t of very low juvenile abundances in 1991. This study shows the dramat ic effect of environmental conditions on early larval survival rates.