The one that did not get away: individual assignment using microsatellite data detects a case of fishing competition fraud

Assignment of an individual to the population from which it most probably o riginated based on its multi-locus genotype has been widely applied in rece nt years. In this study, individual assignment based on microsatellite data was used to identity a case of fishing competition fraud. Despite the fact that the true population of origin was most probably not among the referen ce populations, recent modifications of the assignment tests were used in c onfidently excluding (p < 0.0001) the possibility of a 5.5 kg salmon (Salmo salar) originating from the fishing competition location, Lake Saimaa (sou th-cast Finland). In fact, the probability of the suspect salmon originatin g from one of the regions that supply most of Finland's fish markets was fo und to be over 600 rimes higher than it originating from Lake Saimaa. When presented with this evidence, the offender confessed to purchasing the salm on at a local fish shop and criminal charges were laid. This study emphasiz es the potential practical application of the individual assignment procedu re, in particular the usefulness of confidently excluding populations as th e origin of an individual. A similar strategy could be also used, for examp le in suspected cases of illegal poaching, in order to assign or exclude in dividuals from originating from a claimed population.