Changes in hatchery subsidies of Chinook salmon in the Salish Sea: implications for predators, fisheries, and conservation

Historically, salmon hatcheries were designed to increase fishery production and to recover depleted native populations. As demands of human protein consumption increase and wild populations continue to decline due to anthropogenic impacts like climate change and habitat loss, hatcheries and stocking programs will be called on to provide food security and to supplement threatened populations. Since 1950 over 3.7 billion Chinook salmon have been released into the Salish Sea and its tributaries in Washington State and southern British Columbia. However, relatively little research has been conducted that considers the impact of hatchery subsidies on estuarine and nearshore marine ecosystems in this region. Here, we assessed spatiotemporal patterns of several traits in hatchery-origin Chinook salmon in the Salish Sea over the last 65 years. We found that the average size at release of hatchery Chinook has increased significantly in Puget Sound, but not the Strait of Georgia. Further, it appears the average release date from hatcheries in the Puget Sound and Strait of Georgia have both converged within a common two week window. This could suggest diminished strength of the portfolio effect of hatchery subsidies on the Chinook salmon population complex in the Salish Sea. In this talk, I’ll discuss the implications these changes in hatchery practices could have for conservation of wild salmon populations, predators of salmon, and fishery production in the northeastern Pacific