Where does the cod come from? Panels of gene‐associated markers provide vastly improved origin assignment in Atlantic cod (Gadus morhua)

Methods for determining the geographical origin of individual fish are in high demand for fighting illegal, unreported, and unregulated (IUU) fishing and for independent control of catch certificates and “eco‐labels”. Hitherto, genetic origin assignment of marine fish has been hampered by the general low levels of genetic differentiation among populations.

By using a new concept of studying gene‐associated single nucleotide polymorphisms (SNPs), we show that individual cod can be assigned back to population of origin with unprecedented high levels of precision. We assessed pan‐European variation in more than 1200 gene‐associated SNPs in cod and found that levels of differentiation for a subset of 132 SNPs was best explained by a model including directional selection.

These high‐differentiation SNPs were used for designing “minimum panels with maximum power” for a number of case studies relevant for controlling illegal fishing, ecolabels, and fisheries management. Our results demonstrate how application of gene‐associated markers will probably revolutionize origin assignment in cod by providing faster, cheaper, and more reliable tools for origin assignment