Crayfish are not likely to be confused with any other Missouri animals. The lobster-like body, including the tail fan flattened top to bottom, distinguishes them from their closest relatives in Missouri, two species of freshwater shrimp.
To identify the different species, learn the names of crayfish body parts. Ten appendages are obvious: 4 pairs of walking legs plus 1 pair of pincers (chelipeds) (each pincer has a thumblike movable finger attached to a “palm”). The body is divided into 2 main parts: at the front is the domelike carapace, comprising both head and thorax and to which the legs attach; and the abdomen, which is the obviously segmented hind part of the body, like the meaty “tail” of a lobster. The shallow indentation between the head and thorax is the cervical groove. At the front of the head are 2 types of “feelers”: 1 pair of antennae (the long ones) and 2 pairs of antennules (the short ones). The triangular extension of the carapace between the eyes is the rostrum.
Length (front of head to tip of tail): Depending on species, adult size ranges from 7/8 inch to more than 6 inches. (Length excludes antennae and legs.)
Crayfish occur throughout Missouri, but the greatest variety of species occurs in the Ozarks, where the many separate stream systems carry entirely different species. Some 25 of our approximately 36 crayfish species live in the Ozarks.
Habitat and Conservation
Our diverse crayfish species are adapted to a variety of habitats, including streams with noticeable current; swamps, marshes, and ponds, without currents; caves and springs; and burrowing in the ground, sometimes considerable distances from water, or in temporarily flooded land. Crayfish adapted to permanently flowing streams rarely travel overland; therefore, certain species are fairly restricted to certain drainage systems. Burrowing crayfish tend to live in grasslands and floodplains.
Crayfish are generally omnivores, eating a wide variety of plant and animal materials.
There are about 450 species in North America, and about 36 in Missouri. Twenty-three species are listed as Missouri species of conservation concern, meaning they are imperiled or vulnerable to extirpation from within our borders. On the other hand, other species are robust, prolific, and may be farm-raised for human food or as fish food or bait.
Some crayfish are invasive. Crayfish can be destructive when they are moved from their native ranges (such as native watersheds and river drainages) and introduced to new ones. They can wipe out native crayfish or other organisms when introduced to streams or other areas they don't belong. This is how a crayfish species can be both native to our state yet also invasive. If you care about wildlife and fishing quality, don't move crayfish from one body of water to another.
In Missouri you can harvest any but the protected species, following regulations for live bait. You cannot release crayfish anywhere other than where you caught them.
Mating usually occurs in the fall, and males typically have a different body form, with specialized reproductive structures, in fall and winter. Females usually lay eggs in the spring, adhering them with a gluelike substance to the swimmerets under the abdomen. After hatching, the young remain attached to their mother’s swimmerets until they have completed 2 molts. They then begin making brief forays away from the mother but return to the safety of her abdomen if they feel threatened.
In addition to feeding many types of wildlife, crayfish provide food for many species that humans hunt and fish. Crayfish commonly serve as fish bait, and many people eat crayfish, too. Crayfish are fascinating, colorful creatures in their own right, and part of our rich native heritage.
Crayfish are an important link in the food chain between plants and other animals, breaking down plant materials that are resistant to decay. Crayfish in turn are an important food for many other animals. Presence of crayfish in a stream or pond usually indicates good water quality.