THREATS TO IMPERILED FRESH-WATER FAUNA

Threats to imperiled freshwater fauna in the U.S. were assessed throug h an experts survey addressing anthropogenic stressors and their sourc es. Specifically, causes of historic declines and current limits to re covery were identified for 135 imperiled freshwater species of fishes, crayfishes, dragonflies and damselflies, mussels, and amphibians. The survey was designed to identify threats with sufficient specificity t o inform resource managers and regulators faced with translating infor mation about predominant biological threats into specific, responsive actions. The findings point to altered sediment loads and nutrient inp uts from agricultural nonpoint pollution; interference from exotic spe cies; and altered hydrologic regimes associated with impoundment opera tions as the three leading threats nationwide, accompanied by many les ser but still significant threats. Variations in threats among regions nad among taxa were also evident. Eastern species are most commonly a ffected by altered sediment loads from agricultural activities, wherea s exotic species, habitat removal/damage, and altered hydrologic regim es predominate in the West. Altered sediment loading from agricultural activities and exotic species are dominant problems for both eastern mussels and fishes. However, eastern fishes also appear to be sufferin g from municipal nonpoint pollution (nutrients and sediments), whereas eastern mussels appear to be more severely affected by altered nutrie nt impacts from hydroelectric impoundments and agricultural runoff. Ou r findings suggest that control of nonpoint source pollution associate d with agriculture activities should be a very high priority for agric ultural producers and governmental support programs. Additionally, the large number of hydropower dams in the U.S. subject to federal re-lic ensing in coming years suggests a significant opportunity to restore n atural hydrologic regimes in the affected rivers.