Freshwater mussels are cold, wet and clammy, and their shells may seem more glamorous than the animals inside. But the animals are as distinct as some of their names: fat pocketbook, hickorynut and fawnsfoot are just a few of Missouri’s 69 mussel species.
Most freshwater mussels inhabit clear, free-flowing streams, but they are all descendants of mollusks that lived in salty oceans millions of years ago. Despite their rock-like appearance, they require specific conditions for success. Each species needs clean water of a particular depth and flow, as well as a distinct mix of bottom sand and stones in which to anchor themselves. And the mussel’s life cycle makes a special demand: Each species must have access to a specific “host” animal–most commonly, a particular species of fish–on which the mussel’s young are incubated. The freshwater mussel’s needs are so exact that different species of mussels have been found segregated on opposite banks at the same point on a river.
Habitat disruption quickly affects mussels. Currently, 74 percent of the United States’ 360 freshwater mussel species are in serious decline. Water quality has deteriorated and bank erosion and sediment deposition have degraded streams. The status of mussels is an early warning about aquatic environments.
Nearly half of Missouri’s mussel species are of conservation concern. Because most mussels stay in a single spot their entire lives, they need stable living conditions. Their most serious threat is river damming, which reduces or removes currents necessary to most species.
It’s important to consult Missouri mussel and clam regulations before collecting them. You can also help protect our mussels by joining or forming a Missouri Stream Team in your area. Steam Teams are volunteer groups that monitor water quality and report threats to our rivers and streams.
Get more on mussels with the MDC’s Field Guide.
How Mussels Mature: The Lure and Release Method
Young mussels begin life as nearly microscopic larvae that develop within the hollow gills of their mother. In order to reach maturity these tiny clams must somehow arrive on the gills of a particular species of fish. There, they will attach and live for about 3 weeks as harmless parasites, while transforming their anatomy into that of a juvenile mussel. Only then are they capable of filter-feeding and living an independent existence.
Young mussels must reach a suitable host fish or they die; however, they cannot swim or even crawl. The larval “fish” that are lined up within the gills of the kidneyshell mussel act as a clever ruse to induce a host fish to infect itself with the young mussel–the “lure and release” method.