Why do some fish do it younger than others? learning from experiments

Abstract

Reproductive traits of fish such as age at first maturation or fecundity are not fixed: there is growing evidence that they change through time under the influence of various environmental factors, including fishing. Because these parameters are important in determining population dynamics, a better understanding of these changes is important to fisheries stock assessment. However, field studies are often inconclusive with respect to the ultimate causes of a given change. Although numerous experimental studies have been assessed the influence of environmental factors such as temperature on the reproduction in fish, these generally focus on single factors and do not consider the effects of the origin and individual history of experimental fish. There is scope for the development of ecological experiments to investigate the effects of interacting environmental factors on reproduction at the individual and population levels. This presentation will review experiments that could be used to predict environmental influences in the wild and the limits to such extrapolations. Finally, we will present a set of experiments designed to study maturation reaction norms in fish, i.e. the size at first reproduction as a function of age. We will investigate the effects of genotypes and environmental effects (feeding and temperature) on growth, age at maturity and subsequent spawning performances in reared cohorts.