This project was completed to fulfill PMIS (#89044) which will help UPDE resource managers to make informed recommendations to other management agencies on water flow requirements conducive to the survival of A. heterodon mussels in the upper Delaware River. This project also supports several specific recovery tasks listed in the Dwarf Wedge Mussel Recovery Plan (USFWS 1993). These include Task 1.11: Conduct studies of species' distribution and status; Task 1.2: Identify essential habitat and key areas in need of protection; and Task 4.2: Characterize the species' habitat requirements for all life history stages.