How Is Climate Change Affecting Salmon Returns?

Salmon live intricate lives that span various environments from freshwater to the ocean, both of which are impacted by climate change. Temperatures in the North Pacific ocean have been warm and generally increasing over the last decade, which decreases ocean productivity and the quality of prey food available for salmon at sea, translating to poor growth and survival.

Periods of cooler ocean temperatures, such as the La Niña event of 2020-2023, can increase productivity and lead to better growth and survival for salmon, acting as buffers for the general trend of a warming ocean.
In the Skeena, we are seeing more frequent and intense drought conditions, with low water levels and warm water temperatures in the rivers and streams. Low water levels make it difficult for returning adults to reach spawning grounds, and can result in salmon being stranded in disconnected pools on the edges of rivers. Warm water temperatures are physiologically challenging for salmon and extended periods can cause salmon to die before spawning.

Other climate events can impact survival as well, such as large floods which displace eggs, wash out nutrients and food for young salmon and alter and degrade river habitats. Extreme weather events are projected to be more frequent in the Skeena, which will pose challenges for our fish populations. While these are current challenges, it is important to understand historic and ongoing human impacts. Commercial fishing, artificial enhancement, and habitat degradation have diminished the fine-scale population structure and biocomplexity that would enable salmon to better adapt to climate change.

Climate change is also opening up new opportunities for our salmon, such as new spawning habitats where glaciers have receded, and we are witnessing salmon adapt to the changing environment. Glacier-fed systems tend to maintain cooler water temperatures and will be important habitats for future salmon.