Effects of Surgically Implanting Radio Transmitters in Juvenile Largemouth Bass

Recent advances in the technology of miniature radio transmitters have allowed researchers to study smaller fish, including juveniles, for which behavioral information is lacking. Transmitters selected should have minimal effects on tagged fish so that inferences may be made about untagged individuals. Our objective was to evaluate the short-term effects of surgically inserted dummy transmitters (1.2-2.7% of the fish's body weight) on growth and predator avoidance in 90-120-mm hatchery-reared Largemouth Bass Micropterus salmoides. We compared growth and predator avoidance between tagged and untagged (control) fish in tanks. Mortality of tagged and control fish was variable by tank and was most commonly caused by columnaris, a fish disease widespread in aquaculture. A slight impairment of growth for tagged fish (difference of as much as 1.19% body weight gained per day) was observed during experiments run for 21 and 30 d. At the conclusion of each growth experiment, most fish had shed their suture and incisions had completely healed. No incidents of transmitter expulsion occurred in either growth experiment. During the predation trials, 49% of both tagged fish and controls were eaten by predators, suggesting that the radio tags did not affect the fish's vulnerability to predation. Despite some mortality observed in the laboratory and slight growth impairment in tagged fish, predation studies implied that the ability to avoid predators was not affected in tagged individuals. Therefore, we conclude that surgical implantation of radio transmitters can be a valid tagging technique for examining the behavior of juvenile Largemouth Bass in short-term field studies. Received June 14, 2013; accepted October 7, 2013