Acoustic tagging effects on juvenile sockeye salmon swimming performance, growth, post-surgical wound healing, survival, and metabolic rate in freshwater and saltwater

Juvenile Pacific salmon make large-scale migrations from natal freshwater rearing grounds to the Northern Pacific Ocean. To properly manage these species an understanding of their migration patterns and survival is necessary. Acoustic telemetry is an ideal tool used to study the migratory survival and behavior of juvenile salmonids. However, the assumption that tagged individuals behave similarly to non-tagged conspecifics in the freshwater and saltwater phases of their outmigration need to be validated as part of large-scale telemetry studies. Consequently, a laboratory-based experiment was carried out to evaluate intracoelomic tagging effects on juvenile sockeye salmon (Oncorhynchus nerka) swimming performance, growth, post-surgical wound healing and survival in both freshwater and saltwater. A sub-set of fish were tagged with three differently sized tags and the response of the fish to tagging was compared to both a sham surgery and non-tagged treatment group. Fish with tag burdens greater than 6 – 8% body weight (BW; tag weighed in water) resulted in some freshwater mortality and decreased freshwater prolonged swimming performance. Fish implanted with larger tags had decreased survival in saltwater and poorer post-surgical wound healing than fish implanted with smaller tags. To minimize the negative effects of intracoelomic tagging, this research suggests that tag burdens should not exceed 6 – 8% BW in juvenile, hatchery-reared sockeye salmon. Oxygen consumption rates were measured during the transition from freshwater to saltwater to investigate the hypothesis that intracoelomic tagging affects metabolic rate in juvenile salmonids during this period. Respirometer experiments during periods of rest and recovery post-swimming were used to assess metabolic rate in freshwater and saltwater for both tagged and non-tagged treatment groups. There was no effect of intracoelomic tagging on recovery metabolic rate post-swimming. However, tagging and salinity had an affect on resting metabolic rate; when fish transitioned from freshwater to 9 ppt saltwater, resting metabolic rate significantly increased. Resting metabolic rate at 9 ppt was elevated in comparison to the lowest resting metabolic rate recorded in saltwater at 28 ppt. However, both non-tagged and tagged fish were able to recover metabolically after transitioning to saltwater, indicated by similar metabolic rate values in saltwater as in freshwater.Forestry, Faculty ofGraduat