Ecological Flows of Freshwater Fishes and Mussels

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Ecological Flow Needs of the Federally Endangered Dwarf Wedgemussel

dwarf wedgemussel

The National Park Service shares management responsibility for aquatic resources in approximately 114 miles of the mainstem Delaware River in New York, Pennsylvania, and New Jersey, including 73 miles within the Upper Delaware Scenic and Recreational River (UPDE) and 41 miles within the Middle Delaware Scenic and Recreational River portion of the Delaware Water Gap National Recreation Area (DEWA). Although the mainstem Delaware is technically a free-flowing system, flow through the parks can be highly regulated by hydropower and water supply operations located in the major tributaries of the upper basin, particularly during low-flow summer months. Of concern to the National Park Service are proposed changes to water management that may impact three known populations of the federally endangered dwarf wedgemussel (Alasmidonta heterodon) within UPDE.

Bovee et al. (2007) and Cole et al. (2008) have recently developed models that describe the effects of river discharge on hydrologic and hydraulic conditions at the three known dwarf wedgemussel sites within the upper mainstem Delaware. There is no information, however, on the physiological needs or environmental tolerances of dwarf wedgemussels that would allow interpretation of how these forecasted conditions will affect mussel survival, health, or reproduction, and under which conditions dwarf wedgemussel populations will likely thrive or perish. Without this information, it is difficult for the NPS to recommend a preferred flow option to the DRBC to protect this resource. The goal of this project is to fill this data gap by determining the biological response of mussels and their host fish to physical parameters affected by flow, and to incorporate that information into a decision support system (Bovee et al. 2007) to assist the NPS in making informed recommendations to the DRBC on ecological flow needs for the parks.


Ecological flow needs of eastern brook trout in the upper Chesapeake Bay watershed:

The historical distribution of brook trout (Salvelinus fontinalis (Mitchill, 1814)) has been heavily fragmented by anthropogenic stressors and their status in large portions of their range is unknown. Brook trout are native to the eastern United States inhabiting small, coldwater streams that drain minimally disturbed watersheds. Small streams are dominated by stochastic processes often driven by hydrologic controls. Moreover, brook trout food resources, including benthic macroinvertebrates, are strongly affected by hydrologic processes. Thus, to better conserve and restore brook trout populations a better understanding of the ecological flow requirements of brook trout and associated fauna are needed. This project will identify habitat suitability criteria for brook trout and associated fauna and quantify habitat availability under a suite of flow events.



Upper Delaware River riverine environmental flow decision support system (REFDSS)


Relevant Publications:

Cole, J.C. 2007. Predicting flow and temperature regimes at three Alasmidonta heterodon locations in the Delaware River. Thesis in Applied Ecology and Conservation Biology, Frostburg State University, Frostburg, MD. 172 pp.

Hanson, L., Schrock, R., Waddle, T.J., Duda, J.J., and Lellis, W.A. 2009. USGS river ecosystem modeling. Where are we, how did we get here, and where are we going? A report from the USGS River Ecosystem Modeling Work Group. U.S. Geological Survey Scientific Investigations Report 2009-5018, 81 p.

Maloney, K.O., W.A. Lellis, R.M. Bennett, and T.J. Waddle. 2012. Habitat persistence for sedentary organisms in managed rivers: the case for the federally endangered dwarf wedgemussel (Alasmidonta heterodon) in the Delaware River. Freshwater Biology 57:1315-1327.

Alley, W.M., E.J. Evenson, N.L. Barber, B.W. Bruce, K.F. Dennehy, M.C. Freeman, W.O. Freeman, J.M. Fischer, W.B. Hughes, J.G. Kennen, J.E. Kiang, K.O. Maloney, M. Musgrove, B. Ralston, S. Tessler, and J.P. Verdin. 2013. Progress toward establishing a national assessment of water availability and use. U.S. Geological Survey Circular 1384, 34 p.

Talbert, C., K.O. Maloney, C.L. Holmquist-Johnson, and L. Hanson. 2014. User’s manual for the upper Delaware River riverine environmental flow decision support system (REFDSS), Version 1.1.2: U.S. Geological Survey Open-File Report 2014–1183, 23 p.

Maloney, K.O., C.B. Talbert, J.C. Cole, H.S. Galbraith, C.J. Blakeslee, L. Hanson, and C.L. Holmquist-Johnson. 2015. An integrated riverine environmental flow decision support system (REFDSS) to evaluate the ecological effects of alternative flow scenarios on river ecosystems. Fundamental and Applied Limnology/Archiv für Hydrobiologie 186:171-192.

Galbraith, H.S., C.J. Blakeslee, and W.A. Lellis. 2015. Behavioral responses of freshwater mussels to experimental dewatering. Freshwater Science 34:42-52.

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