Evaluating Passive Integrated Transponder Tags for Marking Mottled Sculpins: Effects on Growth and Mortality

Abstract

We examined the efficacy of marking mottled sculpins Cottus bairdii with passive integrated transponder (PIT) tags in a 28-d laboratory study. A 2 × 3 factorial experiment was used to compare growth and mortality of tagged fish with those of a control group (i.e., not injected with tags) among three size-classes (55–59, 60–69, and ≥70 mm total length [TL]). Fish were measured on the day of tagging and each week thereafter. Among 26 tagged fish (56–83 mm TL), both survival and tag retention were 96% or greater. Survival was 100% among 25 control fish (56–85 mm TL). Instantaneous growth rates (calculated on a cumulative basis for each sampling period based on mass) for tagged fish were significantly lower than those for control fish during the first 14 d, suggesting that mottled sculpins recovered from PIT tagging after 14–21 d. Additionally, fish size did not significantly affect the instantaneous growth rate of PIT-tagged fish relative to that of the control group. More importantly, we found (on the basis of instantaneous growth rates) that on average, the maximum difference in mass between tagged and control fish was less than 4% among sampling periods for each size-class. Our results suggest that PIT tags are a viable technique for marking small fish and have minimal impacts on growth and mortality.