Evaluation of Internal Tag Performance in Hatchery-Reared Juvenile Spotted Seatrout

Abstract

Stock enhancement programs rely on the ability to recapture and identify stocked fish to evaluate stocking effectiveness. Since 2006, the Seatrout Population Enhancement Cooperative (SPEC) has released almost 600,000 Spotted Seatrout Cynoscion nebulosus, about 100 mm TL, tagged with opercular coded wire tags (CWTs) into coastal Mississippi waters. However, only about 50 fish have been recaptured and initial retention of the opercular CWT has rarely exceeded 75%. This study first evaluated the suitability of visible implant alpha (VIA) and visible implant elastomer (VIE) tags for use in juvenile Spotted Seatrout. The VIA tags performed poorly. Based on those results, the study evaluated the effects of tagging site and fish size on survival, growth, and retention of CWTs and VIE tags and VIE tag fragmentation in juvenile Spotted Seatrout. Three separate growth experiments with juvenile Spotted Seatrout that had mean initial TLs of 93, 138, and 152 mm, respectively, were conducted to assess the effects of tagging. Each growth experiment had nine treatments consisting of a control, fish with either an opercular CWT, a dorsal muscle CWT, a ventral caudal fin VIE tag, or a jaw VIE tag, and four false-tagged treatments corresponding to each tagged treatment. Dorsal CWTs were retained better than opercular CWTs; VIE tags were equally retained regardless of body location. However, VIE tag quality was affected over the long term by pigmentation overlap and fragmentation. Growth rates and survival were not different within any size-class experiment or among treatments. This study has shown that CWTs and VIE tags are effective marking methods for juvenile Spotted Seatrout.

Received October 11, 2012; accepted May 16, 2013

ACKNOWLEDGMENTS

We thank the Science Consortium for Ocean Replenishment (SCORE) and the Mississippi Tidelands Trust Fund for funding this project, and the Seatrout Population Enhancement Cooperative (SPEC) staff (J. Snawder, A. Apeitos, B. Schesny, and J. Lemus) for assistance. We thank Northwest Marine Technology, Inc. for assistance in the use of their products. We also thank J. Lotz for serving on the lead author's graduate committee and a number of graduate students who sacrificed their time to help us with this research.