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Allele and genotype frequencies for allozymes of phosphoglucomutase (PGM) differed significantly between populations of the central stoneroller (Campostoma anomalum, Rafinesque) collected from sites above and below impact from industrial activities. The frequencies of the PGM‒A allele and PGM‒AA and PGM‒AB genotypes were significantly less in populations of stoneroller minnows collected from impacted sites than in populations upstream of impact. Stonerollers with these sensitive PGM genotypes and stonerollers with genotypes of malate dehydrogenase MDH‒BB were more sensitive to the toxic effects of copper sulfate than other genotypes under laboratory conditions. These results suggest that individuals with certain allozymes may be more sensitive to the toxic effects of environmental contaminants than those with other genotypes. Selection or elimination of individuals with sensitive genotypes by contaminants may result in a narrowing of genetic diversity in populations and thus increase the susceptibility of these populations to further stress. Electrophoretic determination of genetic structure in fishes appears to be sensitive to changes in water quality and may be a useful tool for monitoring the health of aquatic populations.

Allele and genotype frequencies for allozymes of phosphoglucomutase (PGM) differed significantly between populations of the central stoneroller (Campostoma anomalum, Rafinesque) collected from sites above and below impact from industrial activities. The frequencies of the PGM-A allele and PGM-AA and PGM-AB genotypes were significantly less in populations of stoneroller minnows collected from impacted sites than in populations upstream of impact. Stonerollers with these sensitive PGM genotypes and stonerollers with genotypes of malate dehydrogenase MDH-BB were more sensitive to the toxic effects of copper sulfate than other genotypes under laboratory conditions. These results suggest that individuals with certain allozymes may be more sensitive to the toxic effects of environmental contaminants than those with other genotypes. Selection or elimination of individuals with sensitive genotypes by contaminants may result in a narrowing of genetic diversity in populations and thus increase the susceptibility of these populations to further stress. Electrophoretic determination of genetic structure in fishes appears to be sensitive to changes in water quality and may be a useful tool for monitoring the health of aquatic populations.

Many headwater streams in the midwestern United States were channelized for agricultural drainage. Conservation practices are implemented to reduce nutrient, pesticide, and sediment loadings within these altered streams. The impact of these practices is not well understood because their ecological impacts have not been evaluated and the relationships between water chemistry and fishes are not well understood. We evaluated relationships between water chemistry and fish communities within channelized headwater streams of Cedar Creek, Indiana, and Upper Big Walnut Creek, Ohio. Measurements of water chemistry, hydrology, and fishes have been collected from 20 sites beginning in 2005. Multiple regression analyses indicated that the relationships between water chemistry and fish communities were weak, but significant (P < 0Ð05). Fish communities exhibited negative relationships with ammonium and nitrate plus nitrite and positive relationships with dissolved oxygen, pH, and metolachlor. The strongest observed relationships occurred within those regression models that included a combination of nutrients, herbicides, and physicochemical variables. Multiple regression analyses also indicated that five water chemistry variables exhibited significant relationships (P < 0Ð05) with hydrology. Our results suggest that if water chemistry is the focus of a conservation plan, then the most effective conservation practices may be those that have a combined influence on nutrients, herbicides, and physicochemical variables. Additionally, the use of a combination of conservation practices to address physical habitat and water chemistry degradation is most likely to provide the greatest benefits for fish communities within channelized headwater streams.

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Male and female largemouth bass (Micropterus salrnoides, Lacepede) and bluegills (Lepornis rnacrochirus, Rafinesque) were collected from two power plant cooling reservoirs that received ash pond effluent (Hyco and Catfish Reservoirs, North Carolina) and one that did not (Lake Sangchris, Illinois). Bluegills were also collected from a city reservoir (Roxboro City Lake, North Carolina) that received no industrial effluent. Selenium residues were determined separately in the gonads and in the carcasses of all fish collected. Residues in both carcasses and gonads were significantly higher in fish from reservoirs receiving ash pond effluent. Ovarian selenium concentrations were greater than testicular levels, while concentrations in carcass did not differ between the sexes. Selenium concentrations were significantly higher in the ovaries than in the rest of the carcass in both largemouth bass and bluegills. In males, selenium levels declined in gonads relative to those in the carcass as selenium concentrations in the carcass increased, but no such pattern was evident in females. Bioaccumulation resulted in selenium concentrations 1 ,OOO times higher in the ovaries of bluegills than in the water from which the fish were collected.

Male and female largemouth bass (Micropterus salmoides, Lacepede) and bluegills (Lepomis macrochirus, Rafinesque) were collected from two power plant cooling reservoirs that received ash pond effluent (Hyco and Catfish Reservoirs, North Carolina) and one that did not (Lake Sangchris, Illinois). Bluegills were also collected from a city reservoir (Roxboro City Lake, North Carolina) that received no industrial effluent. Selenium residues were determined separately in the gonads and in the carcasses of all fish collected. Residues in both carcasses and gonads were significantly higher in fish from reservoirs receiving ash pond effluent. Ovarian selenium concentrations were greater than testicular levels, while concentrations in carcass did not differ between the sexes. Selenium concentrations were significantly higher in the ovaries than in the rest of the carcass in both largemouth bass and bluegills. In males, selenium levels declined in gonads relative to those in the carcass as selenium concentrations in the carcass increased, but no such pattern was evident in females. Bioaccumulation resulted in selenium concentrations 1,000 times higher in the ovaries of bluegills than in the water from which the fish were collected.

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