Tennessee’s Treasure Trove of Crayfish

Whether you know them as crayfish, crawfish, crawdads, or mudbugs, just about all of us have encountered these 10-legged aquatic cousins of the crabs and lobsters at some point in our lives.  As children exploring small streams, we discovered crayfish with their menacing claws beneath overturned rocks.  To fishermen, crayfish have long been valued as effective bait for many game fish species such as smallmouth bass and rock bass (redeye).  For many of us, the word crayfish congers up festive images of a Cajun style crawfish boil with potatoes, corn, onions and smoked sausage.  Perhaps recently, you may have even noticed fresh crayfish available in many local grocery stores all across Tennessee.  However, the subject of crayfish is much more interesting than meets the eye or the taste bud for that matter.
 
For example, did you know that freshwater crayfish naturally exist on all continents except Africa and Antarctica?  Currently, there are more than 550 species that occur worldwide, and more than 400 are found in North America. Astonishingly, the state of Tennessee, with at least 78 species may in fact have more crayfish species than any other state!

Crayfish come in a variety of shapes, sizes, and colors and are basically characterized by having a fused head and thorax, a segmented abdomen, and five pairs of legs of which the first pair are usually armed with large claws.  The claws are commonly used for excavating and defense.  The exoskeleton or hard outer surface of the crayfish protect the soft inner body parts and is periodically molted or cast off, as the animal grows.  The eyes of a crayfish are compound and are positioned on stalks that are movable.   Some species of crayfish can become very large such as the Tasmanian Freshwater Crayfish —Astacopsis gouldi, a native to the Australian Island of Tasmania.  This giant can weigh as much as 12 pounds and reach lengths of more than two feet.  Tennessee species fall within a much more modest size range.  The adult Cajun Dwarf Crawfish—Cambarellus shufeldtii— averages about ¾ inch while the largest Tennessee species, the Bottlebrush crayfish—Barbicambarus cornutus—may attain lengths up to 9 inches from tail to claw.

Because of a variety of geological regions that transverse our state from the mountains of the Blue Ridge in the east to the flat coastal plains of the Mississippi Embayment in the west, Tennessee’s crayfish fauna has become richly diverse.  Crayfish species have adapted to live in just about every aquatic environment that exists, such as swamps, streams, and lakes.  However, approximately 12 species spend most of their entire lives within burrows—complicated tunnels excavated and extending down through the soil and eventually into the water table—that may only be detectable by a small mud chimney at the ground surface.  Many of these burrowing species are adorned with beautiful colors of green, blue, red, or orange, while most of the stream dwellers are cloaked with elaborate camouflage exhibiting stripes, saddles, or spots that cryptically blend with the stream substrate.  Tennessee is also home to four cave species that live in complete darkness and have reduced vision or even no eyes at all, and rely on a highly developed sense of smell and touch to survive.  Although the life span of most crayfish species is 2-5 years, unusual species like the cave crayfishes may live for several decades. These special species are particularly vulnerable to pollution and habitat loss.
Crayfish are generally considered omnivorous and may feed on a variety of food items including animal flesh, aquatic insects, and worms.  However, most species feed primarily on aquatic plants and algae.

Reproduction among crayfish species is no less an interesting process.  Following the mating season which often occurs in the fall, the female lays hers eggs which may number as few as ten to several hundred.  She attaches them to the underside of her abdomen with a sticky substance known as glair.  The incubation period may last for several weeks.  Upon hatching the young crayfish will cling to and remain with the mother for protection for one to three weeks before venturing out into the world.

The effectiveness of crayfish as fishing bait has long been known among fishermen.  It’s no wonder that crayfish make such effective bait because some species of game fish rely heavily on crayfish for food.  A few years ago TWRA conducted a study on two East Tennessee rivers, the North Fork Holston and the Nolichucky, which indicated as much as 70% of food items found in the stomachs of larger smallmouth bass and rock bass were crayfish.  Many fishing tackle manufactures have developed various types and sizes of artificial lures that mimic crayfish.  For example, the Rebel Wee Crawfish ®—an excellent crank bait, is available in an assortment of colors and sizes.  Also, a variety of soft plastic crayfish imitations can be jigged or bumped along the bottom and are very effective.  Traditionally however, many fishermen prefer to use live crayfish as a sure fire bait for fishing success.  Typically a hook is simply inserted through the underside of the tail about 2 or 3 segments from the end, and with just enough weight to get the bait down. This natural presentation is an excellent method to entice most game fish species, especially smallmouth bass and rock bass.   Crayfish bait can easily be caught by hand, or any legal fishing method such as traps and seines.  Recently, many bait shops have began offering live crayfish imported from neighboring states.  Because of the threat of introduced species, or non-native species that have become established outside their native range, care should be taken not to release unused bait into the wild.  One species of great concern, Orconectes juvenilis, or the Kentucky River Crayfish, has been widely introduced throughout many river systems in the United States including the upper Tennessee River here in East Tennessee.  This is a particularly aggressive species and is currently replacing some native species.  Perhaps the best source of live crayfish for bait is to catch them in the area one plans to fish.  Crayfish can be legally taken for use as bait in Tennessee with the exception of nine species of crayfish designated as state endangered, one of which—Orconectes shoupi, The Nashville Crayfish—is listed federally endangered.  For more information concerning crayfish and the localities of protected species, please contact the Tennessee Wildlife Resources Agency regional office in your area.

The Region IV Stream Survey Unit is actively surveying crayfish populations statewide in an attempt to document distribution and population status.  Below you will find recent status surveys conducted for some of Tennessee' s threatened or endangered crayfish species along with other useful information.
Tennessee Wildlife Resources Agency
Region 4
Stream Management
Crayfish Resources