Every year, spectacularly colored red Sockeye salmon (Oncorhynchus nerka) return to the rivers of British Columbia to make their arduous upstream Fraser River migration to spawn. An annual spectacle that signals the approaching end of summer. They traverse 400 miles of the Fraser River before passing through an abrupt narrow 115 feet wide span of the river called “Hell’s Gate.” Sockeye salmon can negotiate the churning cauldron of fast water here but what they can’t seem to handle so easily is warmer river temperatures.
Scientists are increasingly worried about higher water temperatures in the Fraser River and the impact it appears to be having on migrating Sockeye. Over the last 60 years, water temperatures in the 1,250-mile long Fraser River have increased significantly. Studies have proven that salmon kept four weeks in 64 °F water had nearly twice the mortality rate of salmon living in 50°F water. Shockingly, this study suggests that sustained elevated river water temperatures can cause severe stress to migrating sockeye and may lead to increased en route mortality Climate change is clearly having an impact as Fraser River temperatures of 64 °F are not uncommon these days.
Sockeye salmon face numerous other natural challenges that have earned them being named as a species at risk, or endangered. In addition to higher water temperatures, such things as commercial fishing, habitat loss, disease and parasites from open-net fish farms. Moreover, they need cool rivers and lakes to survive. Government bodies need to step up their fight against climate change if we are to increase protections for sockeye salmon and hopefully keep them out of hot water.
It’s difficult to know how the next chapter will unfold. During last year’s dominate run, approximately four million fish were predicted to return. However, only 700,000 Sockeye were estimated to have entered the Adams River. This year’s fall run numbered only 3,000 fish despite the forecasted estimate of at least 1.2 million fish. This was the worst return ever for a sub-dominant year; with the next lowest year being in 1939, when only 16,000 Sockeye returned.
Is the end near looming for British Columbia’s iconic annual Sockeye salmon run? Only time, and nature, will tell.