Freshwater Fish - Species

Eastern floater (Pyganodon cataracta)

Description: (Anatomy of a Shellfish)
Shell shape is ovate, subelliptical and elongate, shells of juveniles not very inflated but much more inflated in adult shells, shells are uniformly thin, often with a low post dorsal wing. The Eastern Floater has no hinge teeth or any indication of swellings in this area. Periostracum is light to dark green, rarely becoming brownish or black, often quite brightly colored, with concentric light and dark bands and with dark green rays most distinct on the disc of the shell, broad green rays on the posterior slope are often well developed, giving the area a much darker color. Nacre is bluish-white.

Range: This is a wide-ranging species and is found in South Carolina from the Savannah, Cooper-Santee, Pee Dee, and Waccamaw River basins.

Average Length:  135 mm

Life Expectancy:  Approximately 1-7 years

Preferred Habitat

Mussels were historically abundant in most permanent rivers and streams in North America. Sometimes, mussels can be found in temporary bodies of water such as sloughs and oxbow lakes, that occasionally receive water from rivers during flood events. Mussels are not usually found in streams that experience frequent drying or dry periods of long duration. 

Food Habits

  • Eastern floater are filter feeders that remove particles from the water. 
  • They feed primarily on phytoplankton (algae), which they filter from the sandy or muddy bottom of streams, lakes, or canals.


  • In most species of freshwater mussels, the sexes are separate. Males release sperm into the water column, and females take in the sperm when filtering the water.
  • Fertilization occurs internally, and the female mussel remains gravid, anywhere from several weeks to several months.
  • Most species of larval mussels, called glochidia, must undergo a parasitic stage in which they attach to the gills or fins of a fish in order to complete development. Some mussel species can use a variety of different fish species as hosts, while others are limited to one or very few fish species.
  • In order to increase their chances of finding a suitable host, many female mussels grow an extension of the mantle flap that looks like a small fish, crayfish, insect, or worm to attract a predatory fish host. When the fish attacks, the female releases her glochidia at just the right time.

Literature Cited

US Geological Survey. NAS Nonindigenous Aquatic Species

Bogan, A. E., J. Alderman, and J. Price. 2008. Field guide to the freshwater mussels of South Carolina. (Adobe PDF - 2MB) South Carolina Department of Natural Resources, Columbia. 43 pages