Hatchery Production and Mark Rates of Juvenile Salmon Stocks Along the West Coast of North America: Which Fish Are Truly Wild?

There is increasing concern globally about the potential negative impacts of hatchery salmon on wild fish, especially for depressed populations of Atlantic (Salmo salar) and Pacific (Oncorhynchus spp.) salmon. A fundamental requirement for field investigations of hatchery-wild interactions is determining which individuals are hatchery fish and which are wild. For Pacific salmon, mass marking programs ‘mark’ hatchery fish by clipping their adipose fins. Mass marking allows visible identification of hatchery fish and supports mark-selective fisheries (where unmarked or wild fish must be released). However, not all regions have adopted mass marking management policies and those that do rarely clip 100% of fish, resulting in the release of millions of unmarked hatchery fish annually. We used the Regional Mark Processing Center’s database to compile stock-specific hatchery production and mark rate data for Chinook and coho salmon and steelhead released from hatcheries along the West Coast of North America during 1997-2013.  Our analysis shows that overall hatchery production and mark rates are highly variable between regions and stocks, but mark rates have generally increased over time. This information will help salmon researchers better understand whether the unclipped fish they catch are truly wild or likely to be unclipped hatchery fish.