Tagger effects in aquatic telemetry: Short‐term and delayed effects of surgery in Atlantic Salmon smolts

Impact statement We describe a case study where fish survival and in‐river performance differed markedly between fish that were tagged by two surgeons who followed the same surgical procedure. Moreover, the tagger effect was more pronounced for small fish and fish that were tagged during the morning (relative to the afternoon). Our results remind researchers and managers using telemetry to always consider how handling procedures might influence results and inferences about the study population.