Comparison of Two Methods for Implanting Passive Integrated Transponders in Rio Grande Silvery Minnow

Abstract

Uniquely tagged animals provide an opportunity to study changes in population demographics and movement. Passive integrated transponder (PIT) tags are used to monitor growth, movement, and survival of fishes. Laboratory studies of tag retention and mortality in small-bodied, warmwater cyprinids after insertion of PIT tags are rare. Mortality induced by two PIT tag implantation methods was compared, and tag retention after implantation was assessed. Relations between standard length and tag retention and between standard length and survival in Rio Grande silvery minnow Hybognathus amarus were examined. Fish were randomly selected and PIT-tagged with 12.5-mm tags via surgical incision or needle injection and were held in laboratory aquaria for 32 d. Mean (±SE) survival on day 32 was 99 ± 1% for control fish, 87 ± 6% for fish that received tags by incision, and 50 ± 5% for fish that received tags by injection. We also tagged 280 fish by incision and held them in aquaria for 49 d. On day 49, survival and tag retention were both 90%. Longer fish had higher survival, but tag retention was not related to fish length. Rio Grande silvery minnow can be reliably tagged with PIT tags if the fish are greater than 60 mm standard length. Treatment with antibiotics and holding of fish in captivity for a minimum of 6 d before release are recommended.