Summary:
Using multiple biological markers to establish the fingerprint of a harvest location, individual cod Gadus morhua L. can be classified to their population of origin without error. A combined approach to classification using otolith microchemistry, otolith shape analysis, body morphometry, microbacterial assemblages, internal and external parasites, and microsatellite DNA was found to be more powerful than by any single technique. Binomial and multinomial logistic regression analyzes were used to distinguish wild from farmed fish and subsequently to determine the precise harvest origin of each individual. Two new approaches were used: one focusing on optimal or key variables from each discipline and the other using probability values derived on a technique-by-technique basis. Cod from widely separated origins were classified with high (up to 100% correct) placement success. Focusing on the placement of individual fish, this study represents a decisive advance toward identifying fish harvested from protected populations.