Ecological relationship between wild fish populations and Mediterranean aquaculture in floating fish cages

Abstract

Floating fish farms are associated, with important aggregations of wild fish around them. Several studies have shown that there is an important aggregation around all of the Mediterranean farms throughout. The most abundant families are clupeids, sparids, carangids, mugillids and pomatomids, although the dominant species varied markedly among farms and seasons. This important aggregation affects the behaviour and physiology of the local ichthyofauna, and may have important consequences for wild fish populations and local fisheries on a regional scale. Aggregated fish change diet, using aquafeed as main resource, which increases the biological condition but also affects the fatty acid composition, increasing vegetal fatty acids. Floating cages also aggregate post-larvae and juveniles of several pelagic and benthic species which find protection around the floating structures. Wild fish reduce environmental impact on the benthic communities by feeding on the lost food pellets. In addition, protection of this aggregation around Mediterranean fish farms can promote biomass exportation and enhance local fisheries. Therefore, the aggregation of wild fish around fish farms is an important aspect to take into account for coastal managers.