Evaluation of water quality threats to the endangered Okaloosa darter, Etheostoma okaloosae, in East Turkey Creek on Eglin Air Force Base
Jon M. Hemming Nancy D. Denslow R. Weil D. J. Spade M. L. Tongue N. J. Szabo K. Kroll W. B. Tate
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The federally endangered Okaloosa darter (Etheostoma okaloosae) is found almost exclusively on the Eglin Air Force Base in the Choctawhatchee Bay watershed of Florida. Portions of this limited habitat are threatened by smothering with erosional soils, altered hydrology, and impaired water quality. Taken together, these factors have contributed to the endangered status of this fish. The U.S. Fish and Wildlife Service has been working to remove impediments to the recovery of the darter through threat identification and stream segment restoration. One stream reach in particular, East Turkey Creek, has demonstrated potential water quality problems. Preliminary data indicating possible problems have included poor invertebrate bio-assessment scores (IBI), uncharacteristically high conductivity values, and low numbers of Okaloosa darters. For these reasons, the influence of adjacent land uses, including a wastewater spray field, was assessed. Differences in ambient water quality were found between East Turkey Creek and the reference site. 48-h fish exposure experiments showed that critical pathways of toxicity were induced in laboratory-exposed fathead minnows, suggesting that these exposures could interfere with reproduction and growth of
endogenous fish. To better understand the ecological significance of these preliminary findings, a longer exposure regimen with surrogate fish showing reproductive outcomes (21 d reproductive test), changes in plasma levels of sex steroid hormones and vitellogenin, and changes in gonad histology would be paramount. The data presented here will be used to focus future analysis and to adapt management strategies to address water quality issues to further recovery of the Okaloosa darter.
U.S. Fish and Wildlife Service
http://www.fws.gov/panamacity/resources/DarterEval.pdf, 1 MB
U.S. Fish and Wildlife Service, Panama City Field Office - Contaminants Program