In situ experimental evaluation of tag burden and gill biopsy reveals survival impacts on migrating juvenile sockeye salmon

Abstract

Although telemetry is commonly used to study fishes, researchers rarely design experiments that facilitate in situ quantification of tagging-related impacts to survival. We experimentally applied high (mean burden = 9.6%) and low (2.6%) acoustic tag burdens and gill clip biopsies to migrating juvenile sockeye salmon (Oncorhynchus nerka). Mortality from release to the last marine receiver array was 1.51 times greater for the high tag burden group (25% surviving) compared with the low burden group (40% surviving). A biopsy effect was limited to the first migration segment (14 km), where mortality was 1.86 times greater for biopsied fish. These results demonstrate the importance of quantifying biopsy and tagging effects when survival estimates are prioritized.