America's Mussels: Silent Sentinels

Jan. 10, 2013
From US Fish and Wildlife Service Endangered Species America's Mussels, or clams, are a group of animals so inconspicuous they are often mistaken for rocks. Lieing on the bottom of lakes, rivers, and creeks, they rarely move and eat by filtering water for microscopic food particles. Even their reproductive life seems boring. The male disperses sperm and the water current carries it to the female where fertilization occurs. But throughout much of North America, and particularly in the Midwest, these rock-like creatures are sending an urgent message. North America has the highest diversity of freshwater mussels in the world. And within North America, historically the Midwest had some of the highest numbers of mussels species. Currently, however, in the Midwest (Minnesota, Wisconsin, Iowa, Missouri, Illinois, Indiana and Ohio) more than half of the 78 known species are classified as Federally endangered, threatened or State species of special concern. No other group of animals in the Midwest is so gravely imperiled. To put this in perspective, The Nature Conservancy reports that about 70 percent of mussels in North America are extinct or imperiled, compared to 16.5 percent of mammalian species and 14.6 percent of bird species. Are mussels so imperiled simply because they're delicate creatures that are on their way out anyway? NO. Although mussels look sedentary, they can move. Many species have adapted to the constantly changing situations in streams and rivers. They can also close their shells to avoid short term exposure to toxins or other unfavorable environmental conditions. Thus mussels are tough creatures that can withstand harsh conditions if those conditions are temporary. The fact that so many species of mussels are imperiled in the Midwest shows that there have been significant, long-term changes to our lakes and waterways. And those changes have been so dramatic that these aquatic species are having trouble surviving. Why Do We Care? Monitors of aquatic health: the presence of diverse and reproducing populations of mussels indicate a healthy aquatic system which means good fishing, good water quality for waterfowl and other wildlife species, as well as insurance that our water is safe. Conversely, when mussel populations are at risk, it indicates problems for other fish and wildlife species, and people too. Ecological value: mussels are natural filters, feeding on algae, plankton, and silts, they help purify the aquatic system. Mussels are also an important food source for many species of wildlife including otters, raccoon, muskrat, herons, egrets, and some fish. Economic value: freshwater mussels have been and continue to be a major economic resource; first in the button industry and now in the cultured pearl industry. Mussels from North American form the nucleus of the cultured pearl industry in Asia.Education and aesthetic value: the study of mussels, their natural history, and habitat requirements provides interesting and important lessons on the interconnectedness of the aquatic system and how species adapt to their ecosystem. Cultural value: Mussels played an important role in the cultural history of prehistoric and recent native peoples of the Ohio and Mississippi River basins. They were used as food and the shells were used for ornamentation, tools, and as a commodity for trade. Indian shell middens (the piles of shells that native Americans have left behind) extend for miles along sites of old villages and encampments along the Mississippi and Ohio Rivers. Biodiversity: Mussels have, and hopefully will continue, to play an important role in our aquatic ecosystems. Considering that less than 20 mussel species are found in most other countries of the world, our North American rivers and streams are truly "rich" with close to 300 species!! Mussels do not get cancer. Researchers want to know why and mussels may have additional values in the future that we cannot now predict. The loss of any of these species will definitely have consequences on how the aquatic ecosystem functions.