Otolith Marking of Juvenile Shortnose Gar by Immersion in Oxytetracycline

Abstract

Oxytetracycline (OTC) has been used to mark a variety of fish species at multiple developmental stages; however, there is little information on batch-marking Lepisosteidae. Juvenile Shortnose Gar Lepisosteus platostomus (53 ± 3 mm TL) were seined from an Oklahoma State University research pond and transported to the Oklahoma Fishery Research Lab. Juvenile Shortnose Gar were exposed to a range of OTC concentrations—0, 500, 600, and 700 mg/L—for 4, 5, or 6 h. Lapillus and sagitta otoliths were examined 14 d postexposure for mark presence and evaluation using fluorescent microscopy. Overall, 93.3% of otoliths exposed to OTC exhibited a mark. Concentration of OTC affected the mean mark quality, whereas duration and otolith type examined did not. However, as concentration increased, so did mortality, suggesting a balance is needed to achieve marking goals. Based on our findings, batch marking of Shortnose Gar can be successful at OTC concentrations from 500 to 700 mg/L for 4–6 h, although mark quality may vary and mortality rates increase at the higher concentrations and longer durations.

Received November 28, 2016; accepted April 4, 2017 Published online June 6, 2017

Acknowledgments

We thank those individuals who assisted with laboratory work and forage collection, including Clayton Porter, Jeff Tibbits, Amie Robison, and Michael Hollie. We thank Kurt Kuklinski, Chas Patterson, and Michael Porta (ODWC) for reviewing an early draft of this manuscript. Financial support was provided by the Oklahoma Department of Wildlife Conservation and the Oklahoma Cooperative Fish and Wildlife Research Unit (Oklahoma State University, Oklahoma Department of Wildlife Conservation, U.S. Geological Survey, U.S. Fish and Wildlife Service, and Wildlife Management Institute, cooperating). This study was performed under the auspices of Institutional Animal Care and Use Committee (IACUC) at the University of Oklahoma’s (R16-003) and Oklahoma State University (AG-14-31). Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.