Effects of surgical implantation of electronic tags in fishes: a review and meta-analysis

Electronic tags have been used for decades and continue to gain popularity. Tags are often implanted in the coelom of fishes, with a substantial body of experimental evidence now assessing the effects of those tags. We revisit a review of tagging effects (Cooke et al. 2011) to provide the most comprehensive review and meta-analysis of intracoelomic tagging effects in fishes to date. We reviewed 295 studies, yielding 226 laboratory trials reporting survival and 215 reporting tag retention. Mean survival in tagged fishes was 88.26% and tag retention was 87.05%. Both metrics were negatively related to tag:body mass ratios (i.e., tag burden), remaining above 90% on average with tag burdens below ~ 3–4%. Substantial heterogeneity existed among studies, with a modest portion of the variability in survival and tag retention explained by family, tag burden or trial duration. Across the tagging effects literature, 42% of papers documented negative effects of tagging on growth, and 34% found reduced critical swimming speeds relative to controls. Progress has been made in addressing some knowledge gaps, but biases in the tagging effects literature remain and only a small fraction of species used in electronic tagging studies are represented. Interest in understanding sublethal endpoints is growing, however, the importance of factors such as sex, reproductive status, sterility, and tag coatings remain poorly understood. Tag burdens of ~ 3–4% appear to balance tag size and unwanted tagging effects. More research is needed to better understand sublethal tagging effects and improve the inferences made from electronic tagging studies.