Freshwater Fish - Species

Eastern pondhorn (or Florida Pondhorn) (Uniomerus carolinanus)

Description: (Anatomy of a Shellfish)
Shell medium to large reaching 114 mm in length. Outline rhomboid or long rhomboid. Valves subinflated or inflated, subsolid. Posterior slope often with two radial sulci. Umbos low to slightly elevated, located in the anterior quarter of the shell. Periostracum is generally black and slightly roughened, but with a satiny sheen over most of the surface. Sometimes the surface is smooth and shiny, especially in the umbonal area, and may then be brownish-yellow or yellowish mixed with green,not rayed. The nacre is white, bluish-white or pinkish to lurid purple

Range: This species is found in all river basins from the Savannah north to the Pee Dee and Waccamaw River basins in South Carolina.

Average Length:  114 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 pondhorn 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.
  • Several studies have shown that they can improve water quality by reducing quantities of excessive algae and nutrients.


  • 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