Fish habitat degradation in U.S. reservoirs Presented by Rebecca M. Krogman Department of Wildlife, Fisheries and Aquaculture Mississippi State University
Acknowledgments • L. E. (Steve) MirandaMississippi Cooperative Fish and Wildlife Research Unit • W. Reed GreenUSGS Arkansas Water Science Center • Kirk RodgersPh.D. Student, University of Arkansas – Little Rock • Many, many state fisheries biologists! • Jeff BoxruckerRFHP Science & Data Committee Chair, Oklahoma Department of Wildlife Conservation (recently retired) • And everyone else at the Reservoir Fisheries Habitat Partnership! • Funding provided by U.S. Fish and Wildlife Service
Construction of large reservoirs • “I think we all agree that the construction of reservoirs has been the greatest single contribution in this century to sport fishing and other forms of outdoor recreation.” • - Brigadier General H. G. Woodbury, Jr., US Army Corps of Engineers
Large reservoirs (>250 acres) National Inventory of Dams 2009
Comparison to natural lakes • Top in purple: Lake Itasca watershed • Bottom corner: Pool 2 of the Mississippi River Credit: Minnesota Pollution Control Agency
Fish habitat issues Delta behind Matilija Dam, California
Effects on fisheries • Habitat availability • Oxygen • Structure • Connectivity • Spawning success • Change water levels • Substrate composition (e.g., gravel beds) • Siltation • Littoral zone vegetation and structure
Effects on fisheries • Larval fish and fingerling survival • Food acquisition • Refuge from predation • Fish productivity • Nutrient dynamics • Availability of zooplankton and macroinvertebrates • Turbidity
Main points • Reservoirs are numerous and ubiquitous • Reservoirs are a product of public policy • Reservoirs are aging • Habitat degradation can affect recreational fisheries
Reservoir Habitat Survey #1 Objective: To document the extent of habitat degradation in reservoirs in the U.S.
Variables • Suspended sediments or inorganic turbidity • Sedimentation • Shoreline erosion • Excessive nutrients • Point-source pollution • Contaminants • Oxygen or temperature stratification • Mistimed water level fluctuations • Insufficient water storage • Excessive aquatic macrophytes • Lack of aquatic macrophytes • Lack or loss of woody debris • Disconnectivity with backwaters • Invasive plant species
Data Analysis • Factor analysis • Interpretation of primary factors and spatial variation • Development of Index of Reservoir Habitat Impairment (IRHI) • 221 respondents 494 waterbodies
New questions • What specific variables are important in each reservoir group? • How can we determine these reservoir groups? • How much of what we see is natural variation?
Reservoirs as part of the landscape “In every respect, the valley rules the stream.” - H. B. N. Hynes, 1975 reservoir
Objective 1 WWF Aquatic Ecoregions • Cluster analysis • Compare clusters to existing classification systems • reservoir classes Develop a classification system for large U.S. reservoirs using impairment factors
Objective 2 • Discriminant analysis • Empirical data • Basin characteristics • Local watershed characteristics • In-reservoir characteristics Validate the classification system using empirical factors
Objective 3 • Ordination techniques to identify reservoirs with a high quality recreational fishery and good habitat • Predictive model development based on high-quality fishing reservoirs Develop a predictive model that assesses fish habitat impairment for each reservoir class
Siltation Excessive suspended sediments or inorganic turbidity Sedimentation Shoreline erosion
Potential Applications • Make quantitative comparisons among reservoirs • Understand geospatial relationships • Guide the decision-making process Fishing below J.T. Meyers Dam
Questions or comments? To learn more about Survey #1 Miranda et al. 2010. Fish habitat degradation in U.S. reservoirs. Fisheries 35(4):175-184. Miranda and Hunt. 2010. An index of reservoir habitat impairment. Environmental Monitoring and Assessment. Published online. In press Hoover Dam.