Nebraskaland

Raising Freshwater Mussels in Nebraska Little known species in need of conservation Story and photos by Julie Geiser 40 NEBRASKAland • APRIL 2017 I f you've ever waded into one of Nebraska's rivers or streams and found a shell, you may have wondered where it came from and questioned what was inside it. Those curious enough will find it came from a mussel, a creature that lives and survives in its own secluded and complex world. Freshwater mussels have evolved in free-flowing river systems for centuries. They play a key role in aquatic environments as they transform the habitat and purify the water. As filter feeders, they process organic matter from the water, which is used to grow their bodies and shells. In return, they excrete nutrients that are used by plant life, invertebrates and fish, providing benefits that extend beyond the water to mammals, birds, and humans. These long-lived species are sensitive to changes in water quality. If mussels disappear, as they have from some Nebraska waters, it is often an indication that something is wrong in their environment. Once gone, so are the benefits they provide. Life History Part of the Unionoidae family, freshwater mollusks – more commonly known as mussels – live in a two-part, hinged shell that grows with the mussel. Shell colors range from yellow-green to black and are sometimes covered in algae, making them hard to spot under water as they blend into their surroundings. They are found in Nebraska's rivers, streams and canals and in some reservoirs. The difference between marine or saltwater mussels and clams is that marine mussels attach to surfaces whereas clams do not. Freshwater mussels are distantly related to marine mussels and clams but they are their own "group" as their reproduction is entirely different from the marine versions. Often called clams, mussels are not clams. Mussels are filter feeders, sucking in water through an incurrent siphon, which is then pumped over the mussel's gills where microorganisms, phytoplankton and bacteria are filtered out for food. Mussels can selectively sort and eject indigestible matter such as small grains of sand and other debris. Water and waste are expelled through an excurrent siphon into the water, where it becomes food for macroinvertebrates that fish feed upon. Large, dense matter accumulates in the mantle cavity as a mass of mucous called psuedofeces, which is periodically ejected by the mussel with a quick contraction of its shell. This filtering ability helps maintain good water quality and supports life in a healthy waterway. Mussels have various muscles that open and close their shell. They also have a muscular foot that they extend from their shell; it is used to slowly pull themselves along the sand, gravel and muddy bottoms of the water in which they live, or to bury and hold themselves in place. This burrowing movement is significant, as it mixes and stabilizes substrates and releases organic matter to the water column. Studies have shown that once an individual mussel has settled into an ideal substrate, it might only travel 50 feet in its lifetime. Others may be forced to move longer distances as habitat conditions change. Some species, in the right The Major Parts MANTLE FLAP GILLS MANTLE EXCURRENT SIPHON INCURRENT SIPHON FOOT ILLUSTRATION BY JULIE GEISER

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