Fraser River Sockeye Fisheries and Fisheries Management - Cohen ...

(e.g., extent of air exposure). Hypoxia causes production of stress hormones and heatshock proteins (Ferguson and Tufts 1992; Furimsky et al. 2003; Iwama et al. 2004) andfurther burdens muscle glycogen stores as well as adenylates; many of which havealready been depleted while the fish struggled in capture gear. Significant levels ofoxidative stress may also occur during recovery. Despite such physiological changes,some fish can recover quickly, but recovery is species- and context-dependent and poorlyunderstood.Stress of capture and release can also change behaviour by either increasing (e.g.,Mäkinen et al. 2000) or decreasing activity (Holland et al. 1993) during the first hoursand days after release. Yet there is little information on behavioural consequences ofcapture on released fish, and no data on Pacific salmon. Large departures frombehavioural norms may indicate physiological stress and impaired ability to forage, avoidpredators, migrate and reproduce (Schreck et al. 1997). Considering salmon areharvested en-route to spawning grounds, behavioural impairments (fallback or delay)could have significant consequences on migration success through exhaustion ofenergetic resources. Despite physiological and behavioural changes that accompany fishcapture and handling, some fish do indeed recover quickly with no fitness consequences;again, such recovery is species- and context- dependent (Cooke and Suski 2005) andgenerally not known for Pacific salmon in freshwater.Research initiated in 2009 was designed to address some of the important knowledgegaps related to post-release survival for Pacific salmon caught in freshwater fisheries.This research has largely been conducted in a collaborative manner involving researchersfrom Carleton University, DFO, Pacific Salmon Foundation, UBC, J.O. Thomas andAssociates, and LGL Limited. Most of the research focuses on the three main capturetechniques used in freshwater salmon fisheries; rod and reel (recreational and FirstNations), beach seine (First Nations), and gillnet (commercial and First Nations). In theFraser River, sockeye are captured and released (or they escape and are thus are releasedunintentionally) via all these gear types. The research has focused on assessing mortalityrates of released fish following various forms of capture or stressor (both in field andlaboratory settings), developing predictive physiological and behavioural indices of postreleasemortality under different thermal experiences, and the development and testing ofrecovery approaches in order to reduce post-release mortality.In a recent study (Donaldson et al. 2011), physiological condition, post-release behaviourand survival of river migrating Fraser River sockeye were examined. Fish were capturedby either beach seine or angling and released immediately, or they were captured byangling and released following a 24-hour recovery period in a net pen. Before release, all58