Freshwater Mussel Restoration

 

In 2007, the Partnership for the Delaware Estuary (PDE) launched the Freshwater Mussel Recovery Program. The purpose of this initiative is to demonstrate how freshwater mussels can be restored, and how the resulting benefits can promote the recovery of an entire watershed. Many species of freshwater mussels once thrived throughout the Delaware River Basin.

The goal of the Freshwater Mussel Recovery Program is to restore the population, diversity, and resilience of mussels through a mix of conservation, habitat expansion, and reintroduction. To this end, the PDE is testing methods for the reintroduction of species into streams where they have disappeared. Reintroduction will be achieved by seeding streams with juvenile mussels from a hatchery, as well as transplanting adults that are reproductively active.

     

Dr. Danielle Kreeger (right) guides members of the Partnership for the Delaware Estuary's staff and various committees on a tour of a Brandywine River survey site following a meeting in July of 2008.

 The Partnership for the Delaware Estuary is studying whether or not freshwater mussels, like these Elliptio complanata specimens, can flourish once again in the rivers of southeastern Pennsylvania. If so, they will help clean local waters

In some cases, conditions may not support the reintroduction of mussels. That is why a key first step in the Freshwater Mussel Recovery Program is to select which streams should be targeted. The PDE team is doing this by monitoring the health of mussels held in underwater cages at prospective restoration sites. Streams will be targeted for reintroduction if these "caged sentinels" show good health after one year. However, if mussels die or lose fitness, that waterway will not be targeted. The first screening study is nearing completion in areas of southeastern Pennsylvania.

It is our hope that the Freshwater Mussel Recovery Program will prove worthy throughout the region and include all native species. By reintroducing native mussel species and, at the same time, boosting current populations, the PDE will improve the ecosystem in the following ways:

  • refilling open niches in the food web
  • providing ecosystem services, or tangible benefits like improved water quality and habitat complexity
  • intercepting and filtering out pollutants before they reach the tidal estuary
  • reassuring the public that ecosystems are indeed being improved
  • preserving imperiled species

Similar to other regions of the United States, freshwater mussels in the Delaware Estuary's watershed are the most imperiled of all plants and animals. All but a few of our 12-to-14 native species are in danger of being wiped out. In fact, even the most common species are disappearing in many streams. This could be the result of a failure to reproduce, an inability to exchange genes among neighbors, or the deterioration of habitat. Whatever the reason for their decline, this spells trouble.

One of the reasons freshwater mussels have declined is their link to fish. They have a complex life cycle during which females nurture their larvae before releasing them onto fish hosts, usually a specific species. If these fish become impaired or restricted in some way (say, by dams for example), so too are mussels affected.

Mussels filter water, enrich the food supply, stabilize riverbeds, and enhance habitat. They also serve as important "indicator" tools for resource managers who are working to assess environmental conditions.

As filter-feeders, freshwater mussels are very sensitive to water quality and habitat degradation. Even if these conditions improve, along with the availability of fish hosts, freshwater mussels cannot rebound quickly. This is due to the fact that they live 50 to 100 years and do not reproduce until at least the age of eight. This, however, does not mean the species is unworthy of attention. On the contrary, this tells us that if we can rebuild mussel beds throughout their natural range, they in turn will help restore the ecology for us, and we will be assured that the system is once again healthy.

The Freshwater Mussel Recovery Program has been made possible thanks to cooperation with the Academy of Natural Sciences of Philadelphia, Cheyney University, Drexel University, and the U.S. Fish and Wildlife Service. Financial support has been provided by ConocoPhillips and the National Fish and Wildlife Foundation. Additional in-kind support has been furnished by the Brandywine Conservancy and U.S. Geological Survey.

If you are interested in learning more about this innovative project, please contact Angela Padeletti at (800) 445-4935, extension 103, or APadeletti@DelawareEstuary.org.