Trace element signature on otoliths and scales for the detection of escaped seabass and gilthead seabream from mediterranean fish farms

Abstract

Significant differences in trace element signature of scales and otoliths have been found between wild and farmed Sparus aurata and Dicentrarchus /abrax in the southwestern Mediterranean. Furthermore, trace element composition in S. aurata scales gave away significant differences between two different fish farms subject to this work. The goal of the present study was to analyze trace element signatura in scales and otoliths of farmed and wild European seabass (Dicentrarchus labrax, Linnaeus 1758) and gilthead seabream ( Sparus aurata, Linnaeus 1758), two commercially important species in the Mediterranean, and test if it is possible to use trace element signaturas in those two tissues as a way to identify escaped farmed fish in the wild. Escapes from sea cages happen far almost all currently sea cage farmed fishes, including the seabass and seabream subject to this study. There are several ecological impacts of escapees on wild populations, and the extent of these impacts has not yet been accurately evaluated. The ability to tell apart farmed from wild fish makes it possible to detect escapees in the natural populations without artificial tagging, which in turn helps to better understand the behaviour of the escapees in the natural environment. This is one of the key steps to take to mitigate the effects of escapes from sea cage farms.