Evaluation of an Alternative Technique for Attaching External Transmitters to Blue Catfish

Abstract

Attaching telemetry transmitters to catfishes (family Ictaluridae) has historically been problematic. Current attachment techniques produce low retention rates or high mortality, or cause altered physiological or behavioral effects. We investigated an alternative attachment technique during three experiments in which external transmitters were fastened to the supraoccipital bone of Blue Catfish Ictalurus furcatus. We hypothesized that attaching a transmitter to the skeletal structure would improve retention rates and minimize negative health effects. In a 2-month pilot study, retention was 100% (N = 20; TL range = 435–638 mm) and fish appeared to be in excellent condition. However, in a subsequent laboratory experiment, retention was poor (41.7% at 2 months and 0% at 6 months; N = 24, TL range = 600–995 mm), which may be attributed to excessive handling during the experiment. The attachment technique was also field tested as part of a larger telemetry study. Fifty Blue Catfish (TL range = 600–995 mm) were tagged and monitored for up to 17 months in Lake Buchanan, Texas. Retention in the field was 40% at 6 months and 19% at 12 months, which was comparable to current free-floating internal transmitter retention rates. Although our procedure produces lower retention than internal transmitters fastened to the pectoral girdle (60–93% annual retention), we believe this modified attachment procedure has future utility despite our mixed results. Our procedure avoids negative health effects (i.e., transmitters absorbed in the intestine or stomach or passed through the body wall) associated with internal tags fixed to the pectoral girdle and has retention rates similar to free-floating internal tags without the need for surgical implantation. Our work demonstrates an alternative transmitter attachment method and suggests future direction (i.e., attaching transmitters to the skeletal structure) in further improving attachment procedures for Blue Catfish.

Received March 12, 2013; accepted June 20, 2013

ACKNOWLEDGMENTS

We thank the many Texas Parks and Wildlife Department employees that assisted with data collection. Editorial comments by staff at Heart of the Hills Fisheries Science Center improved this manuscript. Funding for this project was provided through Federal Aid in Sport Fish Restoration Project F-231-R-1 to the Texas Parks and Wildlife Department.