Needs in the Management of Native Freshwater Mussels in the National Park System

Sue Jennings
Big South Fork National River and Recreation Area

Executive Summary

Freshwater mussels (Phylum Mollusca, Class Bivalvia) have suffered a greater decline than any other wide-ranging faunal group in North America. Because of the decline of mussels throughout North America, many National Park System units are destined to become important refuges for this endangered group of animals. Yet, data on the abundance, distribution, and health of mussel populations in National Park System units are lacking. A preliminary survey of 27 units with mussels indicated that 37% of the responding units did not make baseline inventories. Of the parks with baseline data, 66% of the known mussel species were protected by federal or state laws. Five of the responding units provide a refuge for state and federally listed species: Big South Fork National River and Recreation Area, Buffalo National River, Mammoth Cave National Park, St. Croix National Scenic River, and the C&O Canal. The National Park Service has a critical role in the survival and recovery of freshwater mussel species.

Mussels have important functions in aquatic environments. They are a link in the food chain and help to maintain water quality. Because they are long-lived and particularly sensitive to changes in water quality, mussels are important indicators of aquatic ecosystem health. The disappearance of mussels from a river or lake often signals that other aquatic species are at risk.

North American freshwater mussels have an extraordinary life history and reproductive adaptations. An important feature of their life history is the unique and complex need of the larvae for a fish host to metamorphose from the larval parasitic stage to a free-living juvenile mussel. Freshwater mussels exhibit a variety of shapes from elongated or oval to subcircular, quadrate, or subtriangular. Shells also vary by species in size, thickness, color, shape, and texture. Although freshwater mussels are primarily sedentary, they use a highly muscular and flexible foot for movement, burrowing, or anchoring into the substrate or between rock crevices. Freshwater mussels are suspension feeders, filtering unicellular algae, bacteria, zooplankton, and suspended detrital particles from the water.

Threats to the long-term survival of mussels include: degradation of mussel habitat (sediment loading, erosion, pollutants from improper agricultural, forestry, and mining practices); channelization, dredging and bridge construction; traffic (large vessels or domestic animal crossings); dams or other barriers to fish migration; over-harvest and illegal collecting; and competition from non-native species such as the zebra mussel and Asian clam. Given the preservation goals of the National Park Service and the importance of mussels to aquatic ecosystems, the protection of mussels and their habitats should become integrated in program planning, management, and education by park managers. Protection of water quality and habitats for mussel populations will protect other water-dependent species in parks.

The protection and management of freshwater mussels in NPS units requires:

1 Acquisition of baseline data from inventory, monitoring, and research.

2. Protection and restoration of significant mussel habitats.

3. Prevention of aquatic nuisance species introductions such as the zebra mussel.

4. Restoration of stream banks with native vegetation and establishment of best management practices for land use (forestry, mining, agriculture, and other developments) adjacent to rivers and streams.

5. Inclusion of host fish species management in fisheries management plans.

6. Evaluation of the influences of external activities and habitat alterations on aquatic resources (water quality, fisheries, mussels) and development of strategies for removing or mitigating adverse effects.

7. Development of watershed management plans with local communities, state agricultural agencies, the Natural Resource Conservation Service, and other agencies. Plans should include pesticide and soil best-management practices to reduce erosion, nutrient loading, and other forms of water pollution.

8. Education of park visitors, partners, and adjacent communities about freshwater mussels and protection needs.

Provided as appendixes in this report are a resource bibliography, references for education and outreach materials, and a glossary.

Key words: Mussels, unionoids, mollusks, Bivalvia, management, protection, endangered species, exotic species.

For the full version of this report, please click here.

E-mail comments to the Fisheries Biologist of the Water Resources Division