COHORT SURVIVAL PATTERNS OF WALLEYE POLLOCK, THERAGRA-CHALCOGRAMMA, IN SHELIKOF-STRAIT, ALASKA - A CRITICAL FACTOR-ANALYSIS

A series of age-specific life tables for walleye pollock (Theragra cha lcogramma) in the western Gulf of Alaska was compiled for the 1980-91 year classes. The life tables were utilized to perform an exploratory key factor analysis to examine the timing of critical periods in the r ecruitment process, evidence of density-dependence at different stages and trends in mortality rates. Early larval mortality was significant ly correlated with generational mortality (In recruits/spawning biomas s), but patterns in juvenile mortality also were similar to generation al mortality and in some years were clearly dominant in determining th e fate of a cohort. Density-dependent mortality, based on the correlat ion between mortality and initial abundance, was indicated only for th e late larval to early juvenile stage. Time trends were marginally sig nificant for juvenile mortality. It is speculated that the observed in crease in juvenile mortality is associated with increasing abundance o f arrowtooth flounder. Weaknesses in the data base are discussed; thes e along with the short time series involved make our conclusions tenta tive and subject to further study. We hypothesize that pollock recruit ment levels can be established at any life stage depending on sufficie nt supply from prior stages, a type of dynamics which can be termed su pply dependent multiple life stage control.