Cooperative Fish and Wildlife Research Units Program: Alabama
Education, Research and Technical Assistance for Managing Our Natural Resources

Large instream hydropower dams are required to maintain a minimal level of dissolved oxygen in discharged water, typically determined based on the temperature and oxygen requirements of largemouth bass or other game fishes. However, while we know a great deal about the abiotic and biotic requirements of many game fishes there is a surprising lack of data regarding critical physiological limits of most non-game fishes. A metric that is commonly used to determine hypoxia tolerance of fishes is oxygen (O2) consumption (MO2), which reflects the ability of an organism to extract oxygen from the environment required to maintain routine metabolic rate as DO decreases. Fish species vary in their oxygen consumption and temperature requirements, even though they may coexist in the same river reach. As such, generating predictions as to the effects of temperature and dissolved oxygen variation on entire fish communities below dams is difficult. In addition, many of these fish species serve as hosts for mussel glochidia. Given that many mussels release glochidia during warmer months (>25º C) when fish have higher respiratory demands and are likely more vulnerable to stress caused by variation in water temperature, effects on fishes will also influence mussel communities. Because research is needed to characterize the dissolved oxygen and temperature requirements of ecologically important species, this project is applying respirometry to quantify the dissolved oxygen and temperature requirements of a larger number of non-game fishes in an effort to generate more general predictions that can be used to determine suitable conditions in waters below impoundments. Species from the southeastern US will be selected to determine if specific physiology requirements are linked to taxonomy or habitat requirements. These data will have immediate application to USFWS and other regulatory agencies for determining whether current DO regulations are appropriate for species of concern. Our findings and predictions will assist in decision making for specific projects (i.e., SHC, conservation design, and Alabama’s Strategic Habitat Unit-SHU Project) and will be applicable to delivery of conservation actions relative to impounded river systems and habitats across the region and beyond.