The physiology, behaviour, and fate of up-river migrating sockeye salmon (Oncorhynchus nerka) in relation to environmental conditions in the Fraser River, British Columbia

One of the most challenging phases of the sockeye salmon (Oncorhynchus nerka) spawning migration is the transit through the freshwater environment. I utilized biotelemetry and thermal loggers to identify strong evidence for limited thermoregulatory behaviour of migrants through the Fraser River mainstem, British Columbia. I integrated biotelemetry and biosampling methods to identify the physiological, energetic, behavioural, and environmental factors that characterize individual migration fall back (i.e., anomalous movement down-river following release) and fate (i.e., survival to reach spawning grounds versus en-route mortality), in the freshwater environment. Fall back individuals had elevated stress indices resulting in slowed migration rates. Physiological indices were not predictive of failure to reach spawning grounds, but en-route mortalities were characterized by slowed migration rates. Stock and year effects were found for several variables. Overall, my research contributes novel findings on the basic freshwater migration biology of this species by elucidating the interplay among physiology, migration behaviour, thermoregulatory behaviour, environmental conditions, and fate.