Post-escape dispersion of farmed seabream (Sparus aurata L.) and recaptures by local fisheries in the Western Mediterranean Sea

Abstract

Escapes of cultured gilthead seabream (Sparus aurata L.) have been recorded throughout the Mediterranean Sea. In the current study we simulated escape incidents of seabream tagged with acoustic transmitters (N=38) or external tags (N=2191). Tagged individuals showed both a high dispersion within the first 5 days after release and a high mortality rate (>60%) where the fish appeared to be predated at the release farm. However, some individuals remained not only at the release farm but also at the nearby farm facilities for long periods, surviving up to 4 weeks with a clear diurnal swimming depth behaviour related to farm activity. Local fisheries contributed largely recapturing tagged individuals that disperse from farm facilities (7.25%), being professional trammel-netters the major contributors (71.5%). Those recaptured individuals were caught on usual fishing grounds and habitats where their wild conspecific live (seagrass, sand or rocky bottoms), feeding on natural preys such as crustaceans and molluscs after one week in the wildness. Therefore, our findings emphasize the negative ecological consequences that escapees might entail to nearby cultured and wild stocks, and the importance of local fisheries to reduce the potential effects of escape incidents on natural stocks.