Freshwater mussels (Bivalvia: Unionoida) inhabit many tidal and non-tidal freshwater settings, including natural systems (streams, rivers, ponds and lakes) and novel, man-made systems (stormwater ponds, living shorelines). Globally, there are more than 1,000 species, but they are one of the most imperiled animal groups due to their complex life histories and sensitivity to habitat and water quality degradation. This is concerning because freshwater mussels often exist in dense “mussel beds” that furnish diverse ecosystem services, much like their marine counterparts. For example, mussel beds help stabilize erosion, enrich benthic habitats for other plants and animals, and offset some types of water quality impairments (e.g. excess nutrients, pathogens). Expanding the aquaculture toolkit to include freshwater mussels can unlock opportunities to promote resilience and ecosystem services in a greater array of niches along the river-to-sea continuum, including impaired urban areas that need the greatest attention.
Projects to conserve, restore, or enhance freshwater mussels have been hampered because the causes of declines still exist in many areas, and wild populations are too depleted to supply animals for restoration projects. Fortunately, this problem is being solved by recent advances in hatchery propagation and aquaculture. Hatchery-sourced mussels have been successfully reintroduced and used to augment extant populations. In recent pilot studies, mussels also survived and grew quickly in altered and man-made habitats, such as living shorelines and stormwater ponds, respectively. While promising, some questions remain regarding the magnitude and geospatial extent of the potential ecosystem service uplift from mussel investments. Like their marine counterparts, freshwater mussels tend to aggregate and therefore do not provide universal benefits everywhere. Causes of past mussel declines persist in many areas. Genetic and biosecurity risks need to be carefully managed. Nevertheless, there appears to be no shortage of locations in most watersheds where mussel investments could be viable, thereby expanding the toolkit of nature-based tactics aimed at improving aquatic ecosystem health. Freshwater mussels are also excellent subjects to stimulate community-based science and educational interest in aquatic ecology because they are sessile, long-lived, and can be seeded and monitored in accessible aquatic habitats along the urban-rural spectrum.
Mussel investments for ecosystem services have been largely unexplored because managers, scientists and funders are still mainly focused on rare species conservation in places where they still exist. Regarding ecosystem services, the greatest return on investment will result from working with foundation species in impaired habitats, typically near underserved communities. Once established, mussel beds can be augmented with rarer species, many of which are usually found only within a protective mussel bed. Hence, extending “shellfish aquaculture” to include noncommercial organisms such as freshwater mussels can help promote environmental awareness, water quality, and climate resilience in places that need it the most.