Where did the cod come from?

A new genetic analysis of Pacific cod has identified more than 6000 genetic markers, and demonstrates that their DNA diverges steadily with distance, which is termed “isolation by distance”. The results allow researchers to identify where Pacific cod are caught to within 220 km, even if the unknown Pacific cod come from a population that was not included in the original analysis. This is the first time that this particular technique has been applied to any marine species, following from its original application to identify where poached ivory originated. The new analysis also found pronounced differences in DNA between offshore cod, and the cod in the more sheltered waters of the Salish Sea off Seattle and Vancouver. The new paper was written by SAFS postdocs Daniel Drinan and Kristen Gruenthal, SAFS MS student Mary Fisher, SAFS professor Lorenz Hauser, together with their coauthors from NOAA and WDFW, and appears in the journal Evolutionary Applications.

Capture locations of Pacific cod used in the analysis (triangles), and estimated geographic locations for individual cod (+) from each location based on their DNA, showing the accuracy of assignment to location.
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