Freshwater mussels are important components of many aquatic ecosystems because of their filtering ability which improves water quality. One of the most important species of freshwater mussel in the Chesapeake Bay watershed is the Eastern Elliptio (Elliptio complanata). Freshwater mussel abundance and distribution in the Susquehanna River basin is affected by Conowingo Dam. The hydro-power operations at Conowingo Dam limit the abundance and habitat of freshwater mussels (FERC study 3.16 and 3.19). Because the freshwater mussel life cycle requires a host-fish, in particular the American eel (Anguilla rostrata) for Eastern Elliptio, the lack of migratory fish passage significantly restricts mussel reproduction. Consequently, freshwater mussel species have experienced a reduced geographic range and a decreased presence in the watershed. Because of the continued impact to mussels from operation of Conowingo Dam, the restoration of mussels is a key part of the Settlement Agreement (Conowingo Settlement) between the Maryland Department of Environment (MDE) and Constellation Energy Generation LLC.
Restoring Freshwater mussel communities to improve water quality
This novel initiative will focus on restoring healthy mussel communities to utilize their natural filtering activities to improve water quality. At first glance, mussels seem simple and lackluster, often being mistaken for rocks in the streambed. However, this diverse group of animals has a complex life-history and provides many ecosystem services. Each mussel can filter 10 gallons of water per day, which reduces the transport of nutrients, sediment, and even bacteria downstream and their positive impact reaching the mainstem of the Chesapeake Bay.
The purpose of this initiative is to restore and increase the number and biomass of freshwater mussels to ensure self-sustaining populations that will help reduce nutrients transported annually to the Chesapeake Bay from the Susquehanna River Basin. Increasing the abundance of freshwater mussels will ensure population levels that are self-sustaining to aid in the continued improvement of water quality.
Photo: Floating Cages (MDE-Dr. Mieko Camp)
The Conowingo Settlement Agreement
The
Conowingo Settlement requires Constellation Energy to pay Maryland $4.5 million in funding during the first three years after the effective date of the FERC operating license to assist with the cost of constructing a mussel hatchery and developing the restoration program, as well as continued annual payments to Maryland to support the operation and maintenance costs of the mussel restoration initiative throughout the remainder of the term of the FERC operating license.
Maryland Department of Environment and Maryland Department of Natural Resources partnership
On April 5, 2022, MDE entered into a 5-year Memorandum of Understanding (MOU) with the Maryland Department of Natural Resources (MDNR) to initiate the development of mussel restoration, propagation, stocking, and monitoring plans, including conducting outreach and interstate coordination. MDNR is working on tasks under the MOU including the design and construction of Maryland’s first freshwater mussel hatchery at the Joseph Manning Hatchery in Brandywine, MD and a mobile mussel propagation trailer (MMPT) seasonally stationed at the Susquehanna River State Park for mussel propagation and community outreach. While stationed there, the MMPT can be used to hold broodstock mussels, infest host fish, and start the initial primary culture of juvenile mussels. During a spring and fall deployment, the MMPT has a goal to produce 25,000 juvenile transformations. In 2024, the MMPT produced 18,000 transformations in the spring and 46,000 transformations in the fall season. Additionally, in 2024, 200 visitors interacted with the MMPT and participated in mussel propagation outreach. When not deployed at the state park, the MMPT is used at Joseph Manning Hatchery to provide additional support and capacity for the hatchery-based mussel production. So far, over 70,000 lampmussels have been produced at Joseph Manning Hatchery for site assessments and for staff to test out new culture systems and techniques. Eventually, tens of thousands of mussels will leave the new facility every fall for stocking in the Susquehanna and its tributaries.
Nexus to Conowingo Watershed Implementation Plan (CWIP)
Reductions in the levels of nutrients and sediment will aid in the implementation of the Conowingo Watershed Implementation Plan (or
CWIP). This Plan is a collaborative effort between Maryland, Pennsylvania, and New York state to reduce the nutrient load entering Chesapeake Bay from upstream of Conowingo Dam. Reductions in nutrient and sediment loads can lead to improvements in water quality and in the overall health of Chesapeake Bay and its tributaries.
