Freshwater mussels ( order Unionida) are a diverse group of bivalve shellfish with over 700 species recognized worldwide and nearly 300 species native to North Amer ica. However, freshwater mussels are one of the most imperiled aquatic animal groups, with over 70% of species listed as endangered, threatened, or of special concern. Mussel populations in the Delaware Estuary have similarly experienced decreases in their range, species richness, and overall abundance. Hatchery propagation of mussels is one tool that has been developed to address these issues. While hatchery propagation techniques help to increase mussel production, juvenile mussel grow-out is labor intensive and difficult to scale up to meet conservation need s. Younger and smaller mussels may be transplanted directly into the wild, but older and larger mussels have a better probability of success and are preferred.
Mussel aquaculture typically occurs in a controlled pond with access to floating grow-out systems via floating dock or wading. As infaunal organisms, freshwater mussels require substrate to burrow within. Therefore, juvenile mussels are typically grown in a floating basket with a thin layer of sand and Nitex mesh. Baskets and sand must be cleaned to avoid smothering and maintain adequate flow through the basket. Baskets must be thinned to accommodate greater biomass as mussels grow. Field experiments were conducted to test whether an alternative substrate (chicken grit) and alternative aquaculture gear (floating cages, Fig. 1) can promote faster mussel growth . The two mussel species used for these trials included the Eastern Pondmussel (Saggitunio nasutus) and the Alewife Floater (Utterbackiana implicata ). Early data suggest chicken grit is a useful alternative to sand and provides cost savings on materials and labor due to easy cleaning and recovery . Mussel growth and survival in oyster aquaculture gear without any sediment has also been favorable.
These tests have demonstrated that aquaculture practices and gear developed for marine shellfish can be just as suitable for the culture of freshwater mussels, which will enhance production capacity to meet the growing needs for conservation, restoration and enhancement projects in diverse freshwater ecosystems.