Land use, fishing, climate change, and the decline of Thompson River, British Columbia, coho salmon

Abstract

We investigated a recent, major decline in the abundance of a large aggregate of coho salmon (Oncorhynchus kisutch) spawning in the Thompson River, British Columbia, watershed. We found that the decline could be attributed to a declining trend in productivity likely related to changing ocean conditions, overfishing, and freshwater habitat alteration. Among individual watersheds, rates of decline in adult coho salmon abundance were correlated with agricultural land use, road density, and a qualitative measure of stream habitat status but not with the proportion of land recently logged. The recovery of these populations will require the prudent regulation of fishing, the restoration of salmon producing watersheds, and an improvement in ocean conditions.