Consequences of catch-and-release angling on the physiology, behaviour and survival of wild steelhead Oncorhynchus mykiss in the Bulkley River, British Columbia

Steelhead, the anadromous form of rainbow trout (Oncorhynchus mykiss), is one of the most coveted recreationally targeted salmonids worldwide, and catch-and-release (C&R) is commonly used as a conservation strategy to protect wild stocks. Nevertheless, little research has examined how wild steelhead respond to capture and handling. During a summer-run recreational fishery on the Bulkley River in British Columbia, we used non-lethal blood sampling and radio telemetry to assess the physiological stress response, post-release behaviour, and survival of wild steelhead exposed to either 0 s, 10 s, or 30 s of air exposure, over a range of water temperatures, fight times, and landing methods. Steelhead that were air exposed following landing had greater reflex impairment and moved further downstream immediately following release than fish kept in the water, though there was no observed difference in movement two weeks after capture. Overall, angled fish had significantly greater blood lactate levels than baseline levels (obtained from a subsample of fish dip netted from the river) suggesting a general stress response to angling and handling. Regardless of air exposure treatment, water temperature was positively associated with blood lactate and negatively associated with blood pH. Other variables such as fish body size (mm) and fight time (s) had little influence on any of the physiological or behavioural variables. Estimated 3-day survival of steelhead was 95.5%, with deep-hooking as the primary source of mortality. Over-winter mortality of caught-and-released fish was estimated at 10.5%, with an estimated total pre-spawn mortality of 15.0%. This study is the first to evaluate the factors that influence C&R outcomes in wild steelhead in a recreational fishery. Findings suggest that steelhead anglers should limit air exposure to less than 10 s, and that anglers should be cautious (minimize handling and air exposure) when water temperatures are warmer.