Determinants of growth and selective mortality in anchovy and sardine in the Bay of Biscay

In many exploited marine fish species, older individuals within cohorts often have slower growth rates at age than their younger counterparts, a process generally attributed to fishing. However, environmental changes might also contribute the selective disappearance of faster growing because increasing constraints acting on in suboptimal environments. Using otoliths anchovy and sardine collected each year spring since 2000 Bay Biscay, we measured individuals’ during age-0 catch-up age-1, followed time from 2018 quantify magnitude mortality. We then determined whether variations mortality were related seasonal temperature, food quantity, stock biomass or harvest rate. both there was decline 0 over declined anchovy. Density-dependence had strong effect systematic with large cohort selection has changed favour Moreover, diversifying occurred for species anchovy, years high individuals, those which (environmental variables having more limited effect). sardine, stronger low quantity unrelated this stock’s Though fishing exerted pressure against still even suggesting that be natural affecting these small pelagic forage species. Although similar trophic position, regimes differed due differences dynamics, sensitivity, It therefore hazardous extrapolate responses single anthropogenic factors onto others.