A REVIEW OF THE DISTRIBUTION, ECOLOGY AND POPULATION-DYNAMICS OF AGE-0 WALLEYE POLLOCK IN THE GULF-OF-ALASKA

This review paper synthesizes published research and unpublished data on the abundance and distribution patterns, ecology and population dyn amics of walleye pollock (Theragra chalcogramma) during their first ye ar of Life (age-0) in the Gulf of Alaska. Distribution patterns have b een described using mainly trawl catches, but recently, acoustic metho dology has been employed, especially in examining vertical distributio ns. Although age-0 pollock are found throughout the Gulf, the highest catches occurred west of Kodiak Island. Pollock are pelagic for at Lea st their first 6 months of life but show an ontogenetic increase in de pth distribution superimposed on a pronounced diel vertical migration at a larger size. Daily growth rates are variable depending on year, s eason and area, and growth generally ceases during the winter. The die t of age-0 pollock shifts from mainly copepods in early juveniles to e uphausiids by fail, with epibenthic organisms becoming important durin g the winter months. Feeding occurs mainly at night in surface waters. Age-0 pollock are most frequently associated with gelatinous zooplank ton (medusae) and older pollock. Many predators on age-0 pollock have been identified; the most important are arrowtooth flounder (Atheresth es stomias), adult pollock, puffins (Fratercula spp.), murres (Uria sp p.), harbor seals (Phoca vitulina richardsi) and Steller sea lions (Eu metopias jubatus). Modelling provides some insight into the population dynamics of these juveniles and environmental conditions which intera nnually affect their survival. These results are discussed relative to the importance of age-0 pollock in the recruitment of this species an d to their role in the pelagic ecosystem.