Estimation of Reproductive Potential for Flemish Cap Cod

Abstract

Traditional measures of spawning stock biomass (SSB) may not provide a good indication of the reproductive potential of a stock. In this paper we calculate alternative estimates of reproductive potential for Flemish Cap cod, successively incorporating annual estimates of proportion mature-at-age, estimates of sex ratio-at-age and of the proportion of females which failed to spawn at each age. While the different indices of reproductive potential produced some change in the stock recruit scatter, there was little difference in the relationship between ln recruitment and ln SSB. Indices reflecting the number of age classes in the SSB and the age diversity were calculated. Multiple regressions showed that including information on the number of age classes and diversity of spawners significantly improved the relationship with recruitment for each of the 3 estimates of SSB. This indicates that the presence of a more diverse age composition of spawners, including older fish, enhances the probability of good recruitment.