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UBC Theses and Dissertations

Understanding the consequences of fisheries-related stressors on adult migrating Pacific salmon Donaldson, Michael Ryan


Adult Pacific salmon (Oncorhynchus spp.) are targeted by the recreational, commercial, and First Nations fisheries during their spawning migrations through the Fraser River, British Columbia, Canada. Salmon can escape from each fishery or be released either voluntarily or due to mandate. Despite a high proportion of Pacific salmon released from each fishery, the primary (e.g., catecholamine, corticosteroid), secondary (e.g., metabolic, osmoregulatory, cellular), and tertiary (e.g., behavioural, survival outcomes) responses to fisheries-related stressors remain poorly understood. The overarching hypothesis of this thesis was that fisheries-related stressors displace fish from homeostasis, resulting in primary and secondary stress responses leading to tertiary outcomes, which in turn can be countered by facilitated recovery techniques. A range of fisheries-related stressors resulted in physiological disturbances reflected by primary, secondary, and tertiary stress responses. Telemetry studies revealed delayed mortality for sockeye salmon released following angling and beach seine capture. Survival was lower for sockeye salmon released from invasive gill and tangle net capture treatments relative to beach seine treatments, and this result was population-specific. Laboratory studies investigated the time required for primary and secondary stress indices to recover following fisheries-related stressors. Biologgers showed that heart rate recovery depended on the intensity and duration of the stressor, requiring several hours. A series of indicators of primary and secondary stress, including the expression of genes related to cellular stress and cell maintenance indicated that the stress response and recovery was sex- and species-specific. A three-pronged approach was used to investigate methods for accelerating recovery and promoting survival following capture stress by combining a laboratory-based physiology study, a field-based telemetry study, and a human dimensions survey. While facilitated recovery showed encouraging results and had general support from anglers, improved techniques are required before this approach could be implemented in freshwater release fisheries. Together, these results support my hypothesis and provide evidence for the context-specific nature of the response and recovery to fisheries-related stressors. This thesis highlights that even a brief fisheries-related stressor can have profound consequences on Pacific salmon, as reflected by the tertiary stress response, including mortality.

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