Reproductive strategy of a migratory fish stock: implications of spatial variations in natural mortality

We investigate how the reproductive strategy in a migratory marine fish may be influenced by spatial variations in mortality in early life-stages. In particular, we examine how spawning time and location affect offspring survival and growth. A drift model for early life-stages (eggs to age 1) of the Barents Sea cod is combined with empirical estimates of spatial variation in mortality at two different life-stages. We examine seasonal and inter-annual differences in survival and growth in offspring originating from two spawning grounds, with the central site requiring higher migration distance and hence cost than the northern. When accounting for spatially explicit mortality fields, central and northern spawned offspring have about equal survival, as do early and late spawned offspring. Furthermore, central spawned offspring grow faster and are likely to reach a larger size compared to northern spawned offspring. Our results indicate that the fitness benefit of southward migration in the Barents Sea cod is not mainly due to higher early survival of offspring, but rather due to effects of offspring acquiring a larger size.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author