Deferred costs of compensatory growth after autumnal food shortage in juvenile salmon.

Growing animals are often able to offset the effects of periods of reduced food availability by subsequently undergoing a phase of elevated compensatory or 'catch-up' growth. This indicates that growth rates are not normally maximized even when food is not limiting, suggesting that fast growth may be costly. Here, we show experimental evidence of a long-term deferred cost of compensatory growth after a period of food shortage. Juvenile salmon subjected to a short-lived low-food regime in autumn subsequently entered a hyperphagic phase, leading to complete restoration of lipid reserves and partial recovery of lost skeletal growth relative to controls. However, several months later they entered a prolonged phase of poorer performance (despite food now being freely available), so that by the following spring they were substantially smaller than controls and had lower lipid reserves for their body size. The incidence of sexual maturation in males the following breeding season was also reduced. Salmon thus appear to trade off the benefits of short-term restoration of fat stores prior to winter against long-term performance.