Tennessee’s diverse aquatic environments are home to a variety of fascinating creatures, including freshwater crayfish. These decapods are often referred to as crabs but are distinct from marine species commonly found in oceans. These crustaceans are an integral part of the state’s aquatic biodiversity. They inhabit various freshwater ecosystems, contributing to their health and balance.
Freshwater Crab Species and Habitats
Tennessee hosts a significant diversity of freshwater crayfish, predominantly from the Cambarus genus. The Appalachian brook crayfish (Cambarus bartonii) is common in the eastern parts of the state. This species has a dark brown, lobster-like appearance with a sharp snout and movable eyes. Its prominent chelipeds, or claws, are used for protection and acquiring food, while other pairs of legs facilitate movement.
Cambarus bartonii inhabits the bottoms of streams, creeks, small rivers, and lakes. They often construct burrows, sometimes called “chimneys,” along the water’s edge, thriving in clear, running water and seeking refuge under rocks. Another species, the cavespring crayfish (Cambarus tenebrosus), is a facultative cave-dweller found in various caves and surface locations within Tennessee’s Cumberland Plateau.
The linear cobalt crayfish (Cambarus gentryi) is notable for its striking deep blue carapace, often accented with orange or yellow markings. This species measures about 3 to 5 centimeters in shell length. Cambarus gentryi creates burrows in damp areas near river banks, with some extending up to 2.5 meters in length and nearly a meter in depth. These populations are primarily localized to the Cumberland and Duck river basins in southern Tennessee.
Ecological Significance and Conservation
Freshwater crayfish are important to Tennessee’s aquatic ecosystems. As detritivores and scavengers, they consume dead organic matter, including leaf litter, which helps recycle nutrients in streams and rivers. Their burrowing activities also aerate and enrich the soil along waterways.
These crustaceans serve as a food source for other animals and are indicators of water quality. A decline in native crayfish populations often signals underlying water quality issues within that ecosystem.
Despite their ecological contributions, many freshwater crayfish species face conservation challenges. Nearly half of all crayfish species are categorized as endangered, threatened, or vulnerable. The Nashville crayfish, found exclusively in Mill Creek and its tributaries, was listed as endangered over three decades ago due to its limited range and water quality deterioration from urban development. While some species like Cambarus tenebrosus, Cambarus gentryi, and Cambarus parvoculus are currently stable, they still face potential threats. Habitat degradation, pollution, and climate change impacts, such as extreme weather events, continue to challenge crayfish populations across Tennessee.