The rivers of Tennessee and the southeastern United States are some of the most diverse ecosystems in the world, especially for invertebrates like mussels and crayfish. Crayfish are especially diverse in Tennessee, with at least 70 species inhabiting our waters. Many crayfish species are specially adapted to their environments, and many only inhabit one or two watersheds. The Nashville crayfish is found only in the Mills Creek basin in central Tennessee, while the Chickamauga crayfish is found only in the South Chickamauga Creek basin, which spans four counties in Georgia and Tennessee. These species are of greater conservation concern due to their small ranges or specialized habitat. Like many other native aquatic animals in the southeastern U.S., they are also under threat due to the introduction of invasive crayfish species.
Crayfish, also called crawdads, crawfish, or mudbugs, are commonly used as bait by commercial and recreational fishermen. They are either purchased from bait stores, or caught from the wild by anglers. Often at the end of the day, the bait is released where used, without regard to its original source. Virtually every invasive crayfish species in Tennessee has been introduced by bait bucket releases. Once introduced, non-native crayfish negatively impact ecosystems and can cause economic losses through damage to riverbanks, dams and dikes. Many invasive crayfish species directly prey on native snails, fish, and crayfish, while others eat or destroy aquatic vegetation that provides habitat and food for native fish. Many of the invasive species are very aggressive and outcompete native crayfish species for burrows or cover.
The Tennessee Wildlife Resources Agency lists six non-native crayfish species as warranting particular concern: bigclaw crayfish, Cumberland crayfish, red swamp crayfish, rusty crayfish, virile crayfish, and White River crayfish. Because these species are generalists compared to many of the native crayfish species, they can spread rapidly through a watershed if introduced. Rusty crayfish and virile crayfish have even been documented hybridizing with native species.
The biggest step you can take in preventing the introduction of invasive crayfish is to use them for bait only from the stream that you are fishing, to take only what you need, or to release bait crayfish from the same stream from which you caught them.