Seasonal dynamics of juvenile coho salmon (Oncorhynchus kisutch) in wetlands of the North Thompson River, British Columbia

Freshwater fish such as juvenile salmon often rely on dynamic and diverse habitats. The importance of freshwater wetlands to juvenile coho salmon in large river networks is not well known. We studied three wetland sites along the North Thompson River, British Columbia, Canada, from May 2021 – May 2023 to understand how seasonal variation in wetland connectivity and water quality influence juvenile coho salmon habitat use. We used monthly mark-recapture sampling to estimate juvenile coho salmon abundance. Seasonal dynamics of juvenile coho salmon in wetlands were intertwined with connectivity and abiotic conditions. Age-0 juvenile coho salmon recruited to wetlands during spring high flows and used wetland habitats year-round. Periods of high density and low oxygen were associated with lower growth and abundance. In addition, our study provides information on the timing of juvenile coho salmon use of wetland habitats which can be used to inform habitat managers of times of year that pose the greatest risk and benefits to these fish.