Commercial culture of gilthead bream has raised concerns in the Mediterranean about the impact of escaped fish on natural populations. Most Mediterranean fish hatcheries breed gilthead breams from Atlantic broodstocks due to their shape and growth performance. Escapees from commercial fish farms resulting from culture system failure, accidents or carelessness may affect genetic diversity of wild populations (Miggiano et al., 2005).Gilthead bream is a voracious predator and its introduction may cause reductions in farmed species such as the Atlantic and Pacific salmon in the rivers and coasts of British Columbia and Chile, and Channel catfish and Asian black carp in the United States, and many tilapia species in north and south America (Balart et al., 2009).
Other impacts from the introduction of commercial cultures into coastal areas and bays include ecological problems such as eutrophication (Vergara Martín et al., 2005 in Balartet al., 2009) and the introduction of a broad range of bacterial, fungal and protozoan diseases and parasites (Balart et al., 2009; Ivona, 2006). Such impacts may disrupt local ecosystems (González et al., 2005).
