Missouri is divisible into four principal aquatic regions, each with its own characteristic assemblage of crayfish. Although some species are found in more than one region and others have only a very local occurrence, the regions serve to identify the typical crayfish habitats and centers of abundance. These regions are shown on the accompanying map.
- The Prairie Region is in north and west Missouri. This region supports a limited crayfish fauna of four common species. The prairie crayfish (P. gracilis), a burrowing species, inhabits grasslands and former grasslands, often at considerable distances from any surface water. Another burrower, the devil crayfish (C. diogenes), lives in timbered areas along the courses of streams. The northern crayfish (O. virilis) occurs in just about any prairie stream capable of supporting crayfish. In mud-bottomed streams and shallow sloughs it is joined by the papershell crayfish (O. immunis), and in rocky streams of the eastern prairies the golden crayfish (O. luteus) is present.
- The Ozark Region is in south-central Missouri. The clear rocky streams of this region are the distribution center for 18 species of crayfish. Eight of these species have never been found outside of Missouri, and nine others have only a limited distribution in neighboring states. Ozark crayfish are distributed according to river basins, and species that are abundant and widespread in one basin are often absent from adjacent basins. Examples are the Neosho midget crayfish (O. macrus) in the Neosho (Spring-Elk) river basin, and the saddlebacked crayfish (O. medius) in the Meramec River basin. More generally distributed species include the golden crayfish (O. luteus), the spothanded crayfish (C. hubbsi). Two species of blind, white crayfish are restricted to cave streams of the Missouri Ozarks. These are the bristly cave crayfish (C. setosus) of the western Ozarks and the Salem cave crayfish (C. hubrichti) of the eastern Ozarks.
- The Lowland Region is in southeastern Missouri. This region supports a distinctive assemblage of ten crayfish species. Most of these species inhabit swamps, sloughs and seasonally flooded areas. Although they occur much of the year in surface waters, they exhibit a strong tendency to burrow during the drier seasons. The red swamp crayfish (P. clarkii) and the White river crayfish (P. acutus) are the most common and generally distributed crayfish in these habitats. They occur also in lowland streams and ditches, where they are joined by another common species, the gray-speckled crayfish (O. palmeri). Other crayfish that occur at a few locations in the Lowlands are the one-inch dwarf crayfish (C. shufeldtii and C. puer), the slightly larger shield crayfish (F. clypeata) and the shrimp crayfish (O. lancifer).
- The Big River Region includes the Missouri and Mississippi rivers. Many kinds of fish are characteristic of the channels of these streams, but crayfish occur only as small local populations or stray individuals. A four-inch shrimp (Macrobrachium ohione) was formerly abundant in the Mississippi River, but disappeared about 30 years ago. Several crayfish species characteristic of the other regions are common in sloughs and marshes on the river floodplains. These include the White River crayfish (P. acutus) and dwarf crayfish (C. shufeldtii) along the Mississippi River, and the papershell crayfish (O. immunis) along the Missouri River. The devil crayfish (C. diogenes) is the common burrowing crayfish on floodplains of both rivers.
The harvest of crayfish for food in the United States now approaches 100 million
pounds annually, with most of that coming from the state of Louisiana. This
harvest consists almost entirely of the red swamp crayfish (P. clarkii)
and the White River crayfish (P. acutus). In southern states the raising
of these species involves filling and draining ponds on a yearly cycle. The
ponds are drained in late spring to grow natural vegetation or crops such as
rice that provide food for the crayfish when the ponds are refilled in the fall.
The adults are in burrows during the dry part of the cycle, when the young are
produced. The crayfish grow throughout the fall and winter period when the ponds
are flooded, reaching a marketable size by early spring.
Different techniques and other species appear to be better suited for crayfish farming in Missouri. Since our winter temperatures are too low for crayfish growth, a management strategy is required that takes advantage of the late spring and summer growing season. Ponds are not drained on a regular basis, and a species is used that does not burrow. The northern crayfish (O. virilis) appears to be the species best suited to Missouri conditions. It does well in ponds and reaches a large size. The longpincered crayfish (O. longidigitus) is our largest native species, but its suitability for pond culture is unknown. The papershell crayfish (O. immunis) is very prolific in ponds, and is an excellent bait species.
Use of this article for identifying Missouri crayfish requires familiarity with a few structures not found in more familiar animals. Most of these structures are illustrated in the accompanying diagram. The length measurement used to indicate crayfish size is the distance from the tip of the rostrum to the tip of the tail fan. The gonopods of male crayfish extend forward on the underside of the thorax between the bases of the legs. The length and shape of the tips on these paired structures are sometimes quite different in crayfish that otherwise look quite similar. The areola is an hourglass-shaped area set off by shallow, lengthwise grooves on the middle of the carapace. When the grooves touch for part of their length, the areola is said to be absent. These and other structures mentioned in the crayfish descriptions can generally be seen by the unaided eye or with a lowpower hand lens.
Content revision: 20030724
