Evacuation Times of Radio Transmitters Consumed by Largemouth Bass

Reduction in transmitter size used in telemetry studies have allowed researchers to tag and track fish that are much smaller than could have been tagged previously. Researchers seek information on juvenile or small fish movement, behavior, and survival to better understand recruitment processes. Juvenile or small‐bodied fish that have been tagged have an increased risk of predation, which results in transmitters being consumed. Knowledge about radio transmitter accumulation in a predator's gut and evacuation times are critical for interpreting locations of radio‐tagged fish and their predators. Our objective was to determine what factors influenced the evacuation time of transmitters (0.3 g), implanted in juvenile Largemouth Bass Micropterus salmoides through the digestive system of adult Largemouth Bass that had preyed upon those tagged juveniles. All transmitters ingested by the predators were evacuated within 84 h. A Poisson regression model showed that transit time decreased significantly with temperature and increased with prey length and predator length. The results of this study suggest that miniature radio transmitters (e.g., 0.3 g) do not accumulate in the digestive tract of predators and that after consumption, up to 3 d of behavior (i.e., movement and habitat use) by the predator, movements could falsely be attributed to the juvenile fish. Therefore, if a distinction cannot be made between predator and tagged juvenile Largemouth Bass, we recommend not including information from the final 3 d before cessation of movement when analyzing the behavior of tagged fish. Received June 9, 2014; accepted January 28, 2015