The ability to determine the natal origins of salmon is required to support international treaties such as the Pacific Salmon Treaty and the incipient Convention for the Conservation of Anadromous Stocks in the North Pacific. Although there are numerous successful applications of salmon stock separation, many problems cannot yet be resolved using available methods.
Coho salmon stocks, in particular, are intractable to most stock separation methods.
Two methods are currently used to attempt separation of coho salmon stocks. In the Pacific Northwest and southern British Columbia, numerous hatcheries release CWT-marked coho salmon. In addition, tagging is expensive and has an associated mortality. The second technique uses scale patterns. The conventional approach for developing a DNA marker as a stock separation tool is to use the polymerase chain reaction to amplify mtDNA pieces and then look for variation.