The effects of PIT tagging on the swimming performance and survival of three nonsalmonid freshwater fishes

Abstract

Increased interest in restoring connectivity to fragmented streams has led to the use of PIT tags to measure movement of wild fishes. When used, PIT tags should not overly compromise survival or functional performance, yet there are relatively few studies on the effects of PIT tags on nonsalmonid fishes. As a result, swimming performances, determined by critical swimming velocity, were measured for flathead chub (Platygobio gracilis), creek chub (Semotilus atromaculatus), and white sucker (Catostomus commersoni) subjected to one of the following treatments: control (no surgery or tag), sham (surgery and suture, no tag), small PIT tag (12.5mm intra-peritoneal PIT tag), and large PIT tag (23mm intra-peritoneal PIT tag). Swimming performances were tested immediately before tagging, 1 day after tagging, and 6–7 days after tagging. Retention and survival were also measured after 30 days. The sham and PIT tag treatments did not significantly reduce swimming endurance (repeated measures ANOVA, P>0.05) for any species. Tag retention approached 100% for all three species. Survival did not vary by treatment for flathead chub (100% survival, all treatments), creek chub survival ranged from 65% (large PIT) to 85% (sham), and white sucker survival ranged from 35% (small PIT) to 95% (control). Logistic regression showed that survival of tagged white suckers was not length-dependent. Based on these results, both 23mm and 12.5mm PIT tags appear acceptable for tracking flathead chub and creek chub, though future investigators will have to account for higher mortality of creek chub. PIT tags implanted in the intra-peritoneal cavity are not recommended for white suckers in the tested size range (115–140mm TL); instead, PIT tags could be inserted in dorsal musculature or attached externally, or other marks (visual implant elastomer or alphanumeric tags, Floy tags) could be used.