Migratory bottlenecks as integrators of species- and population-level diversity: the Skeena River estuary, its salmon, and industrial development

We quantify how an estuarine migratory bottleneck supports population- and species- level diversity of salmon. The estuary of the Skeena River is under pressure from industrial development, with two gas liquefaction terminals and a potash loading facility in various stages of environmental review processes at the same time as recent changes to Canadian environmental laws have reduced the timeframe for federal environmental assessments. We conducted a juvenile salmonid sampling program throughout the Skeena River estuary in 2007 and 2013. We captured all species of juvenile salmonids throughout the estuary in both years, and found that areas proposed for development support some of the highest abundances of some species of salmonids. Specifically, the highest abundances of sockeye (both years) Chinook in 2007, and coho salmon in 2013 were captured in areas proposed for development. For example, juvenile sockeye salmon were 2-8 times more abundant in the proposed development areas. Genetic stock assignment demonstrated that the Chinook salmon and most of the sockeye salmon that were captured originated from throughout the Skeena watershed, while some sockeye salmon came from the Nass, Stikine, Southeast Alaska, and coastal systems on the northern and central coasts of British Columbia. These fish support extensive commercial, recreational, and First Nations fisheries throughout the Skeena River and beyond. Our results demonstrate that estuary habitats integrate species and population diversity of salmon, and that proposed development in these areas will threaten the fisheries that depend on these fishes.