Diversity increases stability and opportunity in First Nations salmon fisheries

Biodiversity can dampen the effects of ecosystem variability through diversification of portfolio assets providing the environmental stability that supports economies and cultures. We examined how elements of salmon biodiversity affect interannual catch stability and within-year season length (opportunity) of First Nations fisheries in the Fraser River watershed from 1983 to 2012 across 5 different species of salmon. Stability and opportunity increased in fisheries with access to increasing richness, as fisheries were closer to the ocean, in mainstem fisheries relative to tributary fisheries, and in fisheries downstream of a partial barrier. The importance of different elements of salmon biodiversity on catch stability varied by species. Richness was the most ubiquitous explanatory variable of fishing opportunity across all species. Through a novel application of spatial portfolio theory, this research quantifies the portfolio effect in fisheries across the Fraser and links basic diversity-stability theory to First Nations food security.