Food-dependent individual growth and population dynamics in fishes

It is long since well established that growth and development in fish individuals are heavily dependent on food intake. Yet, this dependence of individual development on food levels has only to a limited extent been taken into consideration when studying fish population and community processes. Using the modelling framework of physiologically structured population models and empirical data for a number of species configurations, how different size-dependent processes may affect fish population dynamics and community structures are reviewed. Considering competitive interactions, cohort interactions will often give rise to cohort cycles driven by an inequality in competitive abilities between differently sized individuals. The addition of cannibalism may dampen these cycles, the extent to which is dependent on life-history characteristics of the cannibals. The circumstance that individuals change their trophic position over their life cycle as a result of an increase in size gives rise to life history omnivory. In such omnivorous systems, food-dependent growth demotes the potential for predatory and prey fishes to coexist. In tritrophic food chains, food-dependent growth in the intermediate consumer may lead to the presence of bistability including sensitivity to catastrophic behaviour. These results shed new light on the drastic decreases observed in the stocks of many marine fish top predators including their inability to recover after fishing moratoria, and on the suggested presence of alternative states in freshwater fish communities