Reproductive success in Atlantic cod, Gadus morhua

Abstract

This research highlights the complexity of the cod mating system while providing an in-depth empirical analysis of reproductive success in Atlantic cod. I performed a comprehensive examination of reproductive success in Atlantic cod, Gadus morhua, at unprecedented temporal resolution, spatial scale, and sample size. The parentage analysis using eight microsatellite markers was performed on 4489 individual larval samples, from 73 wild-caught adults, obtained daily over a 91-day period. Size had a positive influence on all three correlates of reproductive success: the number of offspring fertilized, the quality of offspring produced and the timing of reproduction (i.e. duration and the number of batches). The mating strategy of cod played a critical role in determining the number of offspring fertilized for both males and females. I hypothesized that male size was fundamental in determining its rank within a dominance hierarchy, and subsequently, top-ranked males were able to dominate spawning events resulting in disproportionately high reproductive success. The three large females had unexpectedly low reproductive success, a trend I attributed to there being a lack of suitably sized males in the spawning basin. This research highlights the complexity of the cod mating system while providing an in-depth empirical analysis into multiple metrics of reproductive success.