A Comparison of Cohort Analysis and Catch per Unit Effort for Dover Sole and English Sole

Abstract

Abstract Indices of year-class strength, stock size, and surplus production of female Dover sole (Microstomus pacificus) and female English sole (Parophrys vetulus) were calculated by two methods: Catch per unit effort (CPUE) and cohort analysis. For each species we derived two CPUE indices and two cohort analysis indices based on different age-groups. For Dover sole, both CPUE indices show strong year classes in the early and mid-1940's, declining recruitment in the late 1940's and early 1950's and an increase in strength up to 1962; however, the year by year correlation of the two CPUE indices with each other was not significant. A similar correlation between cohort analysis estimates was significant, however. Both sets of cohort analysis estimates show a gradual decline in female stock size during the 1950's, and a leveling out at a lower level in the 1960's. Catch per unit effort indicates that stock size has increased in the 1970's. These trends in stock size seem to lag behind parallel trends in rec...