Acoustic Tagging Effects on Sockeye Smolt Swimming Performance, Growth, and Survival

With declines in sockeye salmon abundance, researchers are turning to telemetry studies to uncover movements and survival of Pacific salmon smolts during their outmigration to sea.  Resulting data are used to make general conclusions at the population level with an underlying assumption that the tags do not affect behavior, survival, or physiology of fish.  However, little is known about the effects of tagging sockeye salmon smolts.  Fraser River sockeye salmon smolts were internally tagged with one of three acoustic tags (1.1g, 1.6g, 2.9g) to assess freshwater swimming performance, freshwater growth, and survival in both freshwater and seawater.  Smolts with tag burdens of 8% or less maintained swimming for longer durations than smolts with higher tag burdens.  Survival was above 93% for all treatments in freshwater and above 88% for all treatments in seawater.  The mean growth difference in freshwater for all treatments is significantly higher for smolts held in freshwater for 8 days than smolts hels in freshwater for 16 days, suggesting smolts were held for too long in freshwater.  Our research helps to better interpret telemetry studies and guide new research in juvenile survival studies.