Forensic identification of fish farm escapees: the Norwegian experience

Aquaculture management authorities require the ability to identify the farm of origin for escaped fish. Physical tagging is routinely conducted for domesticated animals (e.g. sheep and cattle); however, there are considerable logistical, animal welfare and economic issues that challenge the feasibility of physically tagging all farmed fish. A 'DNA stand-by method' for identification of escaped Atlantic salmon, back to the cage and farm of origin, was established at the Institute of Marine Research in Norway. In addition, proof-of-concept for the method has been demonstrated to be able to trace rainbow trout and Atlantic cod escapees back to their farm source. The combined sampling, genotyping and statistical analysis on which the method is based has been implemented successfully in the identification of fish farm escapees in Norway, resulting in fines for companies found in breach of regulations. This paper reviews the method, its challenges, and some previously considered alternatives. It is concluded that as the method has been successful for the 3 major species farmed in Norway, each with contrasting production logistics including breeding programs, state of domestication, and magnitude of production, the DNA stand-by method can be applicable to identification of fish farm escapees for a wide range of aquaculture species in all regions of the world.