Abstract
The use of non-lethal methods to quantify indices of animal health is an important tool used for wildlife management. In Florida, non-lethal health assessments have not been carried out on sport fish and there is a need for stress and sex hormone profiles on wild fish. Red drum, Sciaenops ocellatus, are part of a significant recreational fishery in Florida and reside in NASA's Kennedy Space Center waters, the oldest fully protected no-take fisheries reserve in the United States.3 The goals of the study were to develop protocol to define "health" and articulate baselines for stress hormone values, glucose and cortisol, and sex hormones 11-ketotestosterone (11-KT) and 17β-estradiol (E2). The objectives of this study were: 1) to evaluate external parameters and determine if red drum are considered healthy according to the Florida Stock Enhancement Research Facility index;1 2) determine seasonal changes in metabolic disturbance by measuring glucose levels; 3) evaluate seasonal variation of sex hormones 11-KT, and E2 and; 4) evaluate seasonal variation in the primary endocrine stress response by measuring cortisol levels. A 50:50 ratio of males to females and an n = 50 for each of three sampling periods, pre-spawning, spawning and post-spawning season were expected. We hypothesized the population will score above 45, in the healthy range of the health index; there will be seasonal variation in 11-KT and E2 according to sex; glucose measurements will have a range due to last consumption of food and possible variations by season or sex; and cortisol measurements will be similar for pre- and post-spawning and may be lower during spawning season due to suppression by the fish to focus on production of sex hormones. External protocol involved collection of body weight and morphometric data, and identification of external parasites and their locations. Skin scrapes and gill clips were examined in the field under a microscope to look for parasites and any possible abnormalities. Red drum are not sexually dimorphic, hence field estimation was recorded and laboratory hormone profiles will validate field assumptions. The internal exam consisted of a blood sample to profile stress and sex hormones during pre, spawning and post seasons. Restraint and handling protocols for adult fish minimized injury during sampling by not using anesthesia and keeping the complete exam less than 12 minutes. Hormones have been analyzed according to the protocol established for sturgeon2 and are currently undergoing analysis. Preliminary analyses of E2 concentrations are higher for females than males during spawning and overall, which was expected. Glucose data have a range of concentrations similar to other teleosts in the literature after similar capture techniques. Comparisons between seasons and sexes will be made for cortisol and 11-KT and will create baseline ranges for the adult red drum on the east coast of Florida. This health assessment is valuable for future comparisons to red drum in adjacent waters and for NASA and Merritt Island National Wildlife Refuge in development of management strategies for their co-managed waters.
Acknowledgements
The authors wish to thank NASA and IHA for financial support of this project; Eric Reyier, Doug Scheidt, Russ Lowers, Donna Oddy, Carlton Hall, Shanon Gann, Karen Holloway-Adkins, and Tim Kozusko for field sampling assistance; Angie Saul, Chad Young and David Westmark from the Florida Fish and Wildlife Conservation Commission for help developing fish handling techniques; Patrick Thompson and Heather Maness from the University of Florida, Department of Aquatic Animal Health for their assistance with the I-stat in the field; Ashley Boggs of the Medical University of South Carolina, & Hollings Marine Laboratory and Heather Hamlin, University of Maine, Department of Aquaculture Research Institute for their guidance running the laboratory samples.
References
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