Survey of Intersex Largemouth Bass from Impoundments in Georgia USA

Abstract

Intersex fish are increasingly being reported worldwide, primarily in rivers that receive treated wastewater, but few studies have investigated intersex in waters that do not receive wastewater. In a recent reconnaissance survey of intersex fish in North America, a high rate of intersex was reported for Largemouth Bass Micropterus salmoides in some southeastern U.S. rivers; however, the occurrence of intersex in impoundments has not been well described, especially on a statewide scale. Therefore, our objective for this project was to survey the occurrence of intersex Largemouth Bass in a variety of impoundment habitats across Georgia. Largemouth Bass were collected from 11 impoundments without direct municipal or agricultural wastewater inputs. Gonads from all male Largemouth Bass were evaluated for the incidence and severity of the intersex condition based on presence and arrangement of testicular oocytes. Overall 48% of male Largemouth Bass collected from impoundments were intersex, which was found in 9 of the 11 impoundments. Among impoundments, incidence of intersex ranged from 0 to 82% of the males sampled and surface area of the impoundment was a significant predictor of intersex incidence. Intersex fish were smaller than normal males, but population-level effects of intersex and causative factors of endocrine disruption in the impoundments remain unknown. The high incidence of intersex males in small impoundments demonstrates that the condition is not confined to rivers and suggests that factors other than those previously associated with intersex (i.e., municipal wastewater) may be involved.

Received March 29, 2013; accepted July 9, 2013

ACKNOWLEDGMENTS

Funding for this projected was provided by the Georgia Water Resources Institute, the University of Georgia Interdisciplinary Toxicology Program, and a University of Georgia Faculty Research Grant to R. Bringolf. We thank the Georgia Department of Natural Resources for fish collections as well as Amos Tuck, Andrea Fritts, Jennifer Johnson, Peter Hazelton, Peter Dimmick, Russell Parr, Emily Roberts, Caitlin Smith, Mike Bednarski, Colin Shea, Andrew Taylor, and Whitney Jacobs for assistance with fish collections, processing, and analysis. This study was conducted under the auspices of the University of Georgia Animal Use Protocol A2010 05-074-R2. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The Georgia Cooperative Fish and Wildlife Research Unit is sponsored jointly by Georgia Department of Natural Resources, the University of Georgia, the U.S. Fish and Wildlife Service, the U.S. Geological Survey, and the Wildlife Management Institute.