Juvenile Salmon Usage of the Skeena River Estuary

Abstract

Migratory salmon transit estuary habitats on their way out to the ocean but this phase of their life cycle is more poorly understood than other phases. The estuaries of large river systems in particular may support many populations and several species of salmon that originate from throughout the upstream river. The Skeena River of British Columbia, Canada, is a large river system with high salmon population- and species-level diversity. 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, providing motivation for understanding the usage of the estuary by juvenile salmon. We conducted a juvenile salmonid sampling program throughout the Skeena River estuary in 2007 and 2013 to investigate the spatial and temporal distribution of different species and populations of salmon. We captured six species of juvenile anadromous salmonids throughout the estuary in both years, and found that areas proposed for development support some of the highest abundances of some species of salmon. 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 if proposed development negatively affects the salmon populations that use the estuary, then numerous fisheries would also be negatively affected.

Estuary habitat associations for juvenile Pacific salmon and pelagic fish: Implications for coastal planning processes

“…Previous research mapping juvenile salmon use of estuary regions found particularly high abundances of juvenile sockeye, Chinook, and coho salmon near the Skeena River mouth, around the Lelu Island and Flora Bank region (Figure ) (Carr‐Harris et al, ). In addition, this area supports more than 40 populations of sockeye and Chinook salmon from throughout the Skeena River watershed (Carr‐Harris et al, , ; Moore, Carr‐Harris, Gottesfeld, et al, ) and encompasses the locations of seven of the eight LNG developments that were proposed for the greater Skeena River estuary (Aurora LNG, ; Exxon Mobil, ; Pacific Northwest LNG, ; Pembina Pipeline, ; Prince Rupert LNG Ltd, ; Province of British Columbia, , ). This study builds on these previous findings to examine how salmon and other pelagic fish are using specific estuary habitat types and locations.…”

“…A 2‐year field study of juvenile salmon and pelagic species and their habitats was conducted in the Skeena River estuary in 2015 and 2016. This research is part of a collaborative research programme with the Lax Kw'alaams Fisheries Program, Skeena Fisheries Commission, and Simon Fraser University examining the estuary phase of juvenile salmon migration in the Skeena River (Arbeider, Sharpe, Carr‐Harris, & Moore, ; Carr‐Harris et al, ; Carr‐Harris, Gottesfeld, & Moore, ; Moore et al, ; Moore, Carr‐Harris, Gottesfeld, et al, ). Previous research mapping juvenile salmon use of estuary regions found particularly high abundances of juvenile sockeye, Chinook, and coho salmon near the Skeena River mouth, around the Lelu Island and Flora Bank region (Figure ) (Carr‐Harris et al, ).…”

“…This research is part of a collaborative research programme with the Lax Kw'alaams Fisheries Program, Skeena Fisheries Commission, and Simon Fraser University examining the estuary phase of juvenile salmon migration in the Skeena River (Arbeider, Sharpe, Carr‐Harris, & Moore, ; Carr‐Harris et al, ; Carr‐Harris, Gottesfeld, & Moore, ; Moore et al, ; Moore, Carr‐Harris, Gottesfeld, et al, ). Previous research mapping juvenile salmon use of estuary regions found particularly high abundances of juvenile sockeye, Chinook, and coho salmon near the Skeena River mouth, around the Lelu Island and Flora Bank region (Figure ) (Carr‐Harris et al, ). In addition, this area supports more than 40 populations of sockeye and Chinook salmon from throughout the Skeena River watershed (Carr‐Harris et al, , ; Moore, Carr‐Harris, Gottesfeld, et al, ) and encompasses the locations of seven of the eight LNG developments that were proposed for the greater Skeena River estuary (Aurora LNG, ; Exxon Mobil, ; Pacific Northwest LNG, ; Pembina Pipeline, ; Prince Rupert LNG Ltd, ; Province of British Columbia, , ).…”

“…Peak abundances of juvenile pink and chum salmon are observed in the Skeena River estuary in early spring (March–May), whereas the peak migration for juvenile sockeye, coho, and Chinook salmon occurs between mid‐May and mid‐June. Some individuals of all species have been captured in the estuary as late as July (Carr‐Harris et al, ). The spring freshet, a period with elevated river discharge and turbidity, generally occurs annually between May 19 and June 29, but timing and discharge vary according to yearly temperatures, snowpack, and spring flooding events (Hoos, ).…”

Phenological Diversity of Salmon Smolt Migration Timing within a Large Watershed

“…Weekly trawl samples were collected at six sites in the estuary of the Skeena River from the beginning of May until the beginning of July in both years (Carr‐Harris et al. ; Moore et al. ).…”