CONTRIBUTIONS OF FOCI RESEARCH TO FORECASTS OF YEAR-CLASS STRENGTH OFWALLEYE POLLOCK IN SHELIKOF-STRAIT, ALASKA

NOAA's Fisheries Oceanography Coordinated Investigations (FOCI) contri butes information to help forecast year-class strength of walleye poll ock (Theragra chalcogramma) in the Gulf of Alaska. Quantitative estima tes of recruitment are obtained from models of stock assessment and st ock projection employing information supplied by FOCI. To generate its information, FOCI convenes specialists in marine biology, physical an d fisheries oceanography, meteorology, and statistics to assemble and analyse relevant biological and physical time series with respect to r ecruitment and processes hypothesized to influence fish survival. Stat istical methods encompass linear and nonlinear regression, stochastic simulation modelling, transfer function time series modelling, and tre e-modelling, regression. The current database consists of 31 years of data, and analyses have identified factors that affect ocean stratific ation and circulation during spring and summer of the fish's birth yea r as being important to recruitment. A conceptual model of the recruit ment process serves as the framework for a recruitment forecast scheme . A stochastic mathematical simulation model of the conceptual model p roduces similarities between simulated and observed recruitment time s eries. FOCI has successfully forecast recruitment observed over the pa st several years.