AFLP and microsatellites as genetic tags to identify cultured gilthead seabream escapees: data from a simulated floating cage breaking event

Genetic discrimination using DNA fingerprinting is rapidly developing for cultured stock and wild fish populations. Microsatellites and AFLPs are being widely used in aquaculture to assign fish or processed fish products, to their claimed origin, paternity or strain. In the present study, 147 AFLP and 4 microsatellite markers were used as genetic tags in gilthead seabream, Sparus auratus. Specimens from two different hatchery broodstocks (one of Atlantic and one of Mediterranean origin) and wild fishes from a natural population were fingerprinted. Putative offspring from these broodstocks were computer-generated, and the confidence in the parentage assignment of their genetic profiles to the hatchery broodstock assessed. The virtual offspring were then mixed with specimens from a natural population to simulate an accidental escape from a floating cage. The risk of false paternity inclusion was evaluated to test the ability to identify either Atlantic or Mediterranean hatchery offspring among wild fish. The method proved to be reliable, and could therefore be used to forecast the impact of fish farm escapees.