Declines of juvenile coastal cutthroat trout and coho salmon over fifteen years in a salmon-bearing stream in the Salish Sea

Pacific salmon are ecologically, economically, and culturally important species indigenous to British Columbia, Canada. Unfortunately, some populations of Pacific salmon have been declining due to climate change, habitat loss, overfishing, and anthropogenic development. As such, considerable resources have been invested to study, restore, protect, and monitor Pacific salmon and their habitat. Since 2004, Lyall Creek, a salmon-bearing stream in the Salish Sea in British Columbia, Canada, has been monitored. Using 2-pass electrofishing, we investigated changes in observed densities over 15 years (2004-2019) for juvenile coho salmon (Oncorhynchus kisutch) and juvenile coastal cutthroat trout (Oncorhynchus clarkii clarkii) that inhabit Lyall Creek. A statistically insignificant but general decreasing trend was observed for juvenile coho salmon densities over 15 years in Lyall Creek. Juvenile coastal cutthroat trout densities in Lyall Creek exhibited a statistically significant decline. More research is required to understand what anthropogenic and environmental factors are negatively influencing Pacific salmon densities in Lyall Creek. Specifically, water availability may be an important stressor affecting these salmon populations.

Automated summary

Research findings show that the populations of juvenile coho salmon and juvenile coastal cutthroat trout in Lyall Creek have decreased to some extent over the past 15 years, with a more significant decline in the coastal cutthroat trout population. Further research is needed to understand the negative influences of human activities and environmental factors on Pacific salmon densities in Lyall Creek.