Crayfish (also called crawfish and crawdads) are among the largest and most common invertebrates in Missouri's lakes and streams. They are an important food for many other animals and have long been popular as a fish bait. Crayfish are an important ingredient of Cajun cuisine. They have the same desirable nutritional qualities as other seafoods, and their popularity with health-conscious mid-westerners is increasing.
This article is written to better acquaint Missourians with these colorful, interesting and important animals by providing information on the kinds of crayfish that occur in our state, their distribution and how to identify them. The reader may also want to consult "Crayfish of Missouri" by Tom R. Johnson (Missouri Conservationist, July, 1978) for an introduction to the general biology of crayfish, "Crayfish Clambake..." by Jim Auckley (Missouri Conservationist, September, 1975) for information on catching and cooking these animals, and "The Crayfishes of Missouri" by William L. Pflieger. Studies now underway are providing new information on Missouri crayfish, and will lead to the publication of a more comprehensive handbook.
A major deterrent to the study and appreciation of crayfish by the nonspecialist is the difficulty in identifying them. The only identification aids currently available are highly technical keys that place heavy emphasis on slight differences in structures (gonopods) in mature males. Fortunately, Missouri crayfish have more readily observed features that can be used in determining the species. Also, many have definite and quite limited distributions, so that the number of species that need to be considered in making an identification from any given area is quite limited.
At first glance, most crayfish look pretty much alike, but closer study reveals that the species differ greatly in size, color and the proportional development of various body parts. These differences are in turn related to the diversity of habits that crayfish have adopted to find food, reproduce their kind and avoid being eaten by predators such as fish and birds.
Let's compare two species of Missouri crayfish to illustrate these differences. The longpincered crayfish (O. longidigitus) is one of the larger North American species, achieving a length of six inches or more from the front of its head to the tip of its tail. In contrast, the Neosho midget crayfish (O. macrus) rarely exceeds two inches in the same dimension. The long-pincered crayfish is olive-tan trimmed with bright red, and its pincers are dark blue-green prominently studded with yellow knobs. The Neosho midget crayfish is a subdued mottled brown and black without bright markings or knobs. The difference in build between them suggests the difference between a bulldog and a greyhound: the stout build and short, heavy pincers of the Neosho midget crayfish contrast sharply with the more slender build and long, narrow pincers of its larger relative. The Neosho midget crayfish is bits-size for any goggle-eye or bass, and it avoids being eaten by burrowing in bravely shoals with its powerful pincers. An adult longpincered crayfish can mount a formidable defense, and boldly prowls the bottoms of bass-laden pools at night in search of food.
The largest and smallest crawdad species found in Missouri are the longpincer (Orconectes longidigitus, left) and the Neosho midget crayfish (Oroconectes macrus).
The longpincered crayfish feeds on a variety of plant and animal materials, both living and dead - including other crayfish. However, the Neosho midget crayfish is definitely not on its menu, since these two species never occur together naturally. They occupy non-overlapping ranges in the southern Ozarks, with the longpincered crayfish confined to the White River and its tributaries, and the Neosho midget crayfish occurring in the adjacent Spring and Elk River drainages.
Missouri has at least 33 species of crayfish, more than most neighboring states. Each species of crayfish occurs only in certain natural settings or habitats that reflect its special requirements; the diversity of crayfish that occur in our state results from the many types of aquatic habitats that are found here. Based on their habitats and requirements, crayfish can be divided into four broad categories:
- Crayfish living in surface streams.
- Crayfish living in swamps, marshes and the shallows of ponds and lakes.
- Crayfish living in burrows away from surface water.
- Crayfish living in underground streams.
These categories overlap to a certain extent. For example, some species occur for much of the year in seasonally flooded pools, but burrow into the bottom as these pools dry up in summer.
Content revision: 20041104
