Freshwater Mussels of Georgia

Introduction

Altamaha spinymussel

Freshwater mussels are one of the most imperiled groups of animals in North America with over 300 species. Approximately 200 of these species are either extinct or vulnerable to extinction within the foreseeable future. 

North American freshwater mussels historically reached their highest diversity in the Southeastern United States, particularly in Alabama (182 species), Tennessee (approx. 130 species), and Georgia (approx. 126 species). One reason that these states contain a diverse mussel fauna is that they share common waters. Georgia is unique in that it is the only state that has three faunal groups including the Interior Basin, Atlantic Slope and the Gulf Slope.
 
Most freshwater mussels have a very unique life cycle beginning when the female mussel releases her larvae (glochidia) onto the gills and fins of suitable fish hosts. To attract host fishes, many mussels display a modified portion of their flesh, which serves as a "lure", often times resembling a small fish, worms, or crayfish. Other mussel species release specialized packets called conglutinates into the water column, which resemble small insects.  The host eats the conglutinate (containing glochidia) and becomes infested on the fish. The parasitic glochidia live on the fish for several weeks depending on water temperature and time of year before transforming into juvenile mussels. The juveniles settle into the river bottom where they remain for their entire life, often ranging between 50-100 years. During this time, mussels feed by filtering microscopic bacteria and algae from surrounding water.

     Mussel life cycle

Although many mussel species still exist, many have become extinct due to poor land use practices, industrial pollution, and the damming of many rivers where these animals once flourished. Dams are one of the main reasons for the loss of native mussels because they transform rivers into lakes and essentially drown the mussels by eliminating the riffle areas that most mussels tend to prefer. Dams also change fish communities in many places, preventing mussels from finding suitable host fish. Poor land use practices have resulted in excess sedimentation, which may "suffocate" the mussels or impede their ability to move in response to conditions in which they may encounter through their relatively long life. Industrial pollution throughout the past 100 years has poisoned many of the streams and rivers where mussels once existed, killing many and preventing reproduction. Find out more about threats to freshwater mussels and other aquatic species on our aquatic threats page.

Mussels are important because they are one of the most sensitive indicator species occurring in our waters. While many fish can move away from polluted stretches of rivers and streams, mussels will remain until they can no longer survive. However, even after water quality improvements are made, mussels are often the last organisms to re-colonize the waters due to their complicated life cycles. Mussels are also an important source of food for many bottom-dwelling fishes and mammals including otters, muskrats, and raccoons. 

Recommended Freshwater Mollusk Websites

Rare Mussel and Snail Species Profiles




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