Fish Health Assessment Index Study of Four Reservoirs in West-Central Georgia

I investigated differences in a modified fish health assessment index (FHAI) among reservoirs, sections of reservoir (lower, middle, and upper), periods (summer 2000, winter 2001, summer 2001, and winter 2002), and species (bluegill Lepomis machrochirus and largemouth bass Micropterus salmoides) in four west-central Georgia Piedmont reservoirs to explore the feasibility of adapting the FHAI in Georgia as an addendum to agency-standardized sampling protocols for identifying problem reservoirs and problem areas in reservoirs. Mean fish health varied significantly over time across reservoirs, sections of reservoirs, and species. Lakewide sampling was necessary to adequately characterize overall reservoir health. Fish health of both species responded similarly to poorer areas; however, fewer bluegills than largemouth bass per sample achieved the same level of precision. The collection of 45 fish lakewide of each species per sampling period yielded a precision level approaching 20–25% of the true fish health mean for largemouth bass and 15– 20% for bluegills; these precision levels had a 1 in 20 chance of being incorrect. Largemouth bass fish health in the upper section of West Point Reservoir was significantly poorer than that in all other reservoirs studied. The top six metrics that correlated most to fish health scores were nearly the same for both species (abnormal kidneys, livers, pseudobranchs, gills, thymuses, and spleens for largemouth bass and pseudobranchs, kidneys, spleens, livers, thymuses, and eyes for bluegills). Period-to-period variability precludes same-site comparisons over time; however, the FHAI appears to be useful in identifying consistently poorer areas in need of further study.