Novel approach for testing the food limitation hypothesis in estuarine and coastal fish nurseries

Abstract : Survival success of early life stages of fish is regulated by density-dependent effects, but the limiting factors explaining these effects have not been well identified. In coastal habitats, juveniles of many fish species occur in high concentrations and possibly compete for food resources. This study compared the ratio of food consumption to benthic prey production to test whether food availability is a major factor defining the carrying capacity of fish nurseries. We developed a method to quantify the exploitation efficiency (also called ecotrophic efficiency) of the juvenile fish feeding on benthic prey, expressed as a ratio of food consumption to food production. This method includes many sources of uncertainty and a key parameter of prey accessibility. Applied to the case study of the Bay of Vilaine (north Bay of Biscay), results suggest food limitation for juvenile fish. The generic nature of this method supports its wide application in various nursery habitats. As food limitation is a density-dependent process having a dampening effect on recruitment variability, examining its occurrence over time and space will improve our comprehension of nursery-dependent fish dynamics