Missouri is divisible into four principal aquatic regions, each with its own characteristic assemblage of crayfish. 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 seven common species. The prairie crayfish (Procambarus gracilis), a burrowing species, inhabits grasslands and former grasslands, often at considerable distances from any surface water. Another burrower, the devil crawfish (Cambarus diogenes), lives in timbered (and formerly timbered) areas along the courses of streams or near ponds. The virile (also called “northern”) crayfish (Orconectes virilis) occurs in just about any prairie stream capable of supporting crayfish. The virile crayfish is probably Missouri’s most widespread species. In mud-bottomed streams and shallow sloughs it is joined by the calico (also called “papershell”) crayfish (Orconectes immunis), and in rocky streams of the eastern prairies the golden crayfish (Orconectes luteus) is present.
- • The Ozark Region is in south-central Missouri. The clear rocky streams of this region are the distribution center for 26 species of crayfish. Eight of these species have never been found outside of Missouri, and 11 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 (Orconectes macrus) in the Neosho (Spring-Elk) River basin, and the saddlebacked crayfish (Orconectes medius) in the Meramec River basin. More generally distributed species include the golden crayfish (O. luteus), and the spothanded crayfish (Orconectes punctimanus). The Missouri Ozarks harbor three species of blind, white crayfish that are restricted to cave or underground streams. These are the bristly cave crayfish (Cambarus setosus) of the western Ozarks, the Salem cave crayfish (Cambarus hubrichti) of the eastern Ozarks, and the Caney Mountain cave crayfish (Orconectes stygocaneyi), which is known from only one cave in southern Missouri.
- The Lowland Region is in southeastern Missouri. This region supports a distinctive assemblage of eleven 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 crawfish (Procambarus clarkii) and the White River crawfish (Procambarus 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 (Orconectes palmeri). Other crayfish that occur at a few locations in the Lowlands are the one-inch, Cajun dwarf crayfish (Cambarellus shufeldtii) and swamp dwarf crayfish (Cambarellus puer), the slightly larger ditch fencing (“shield”) crayfish (Faxonella clypeata) and the shrimp crayfish (Orconectes 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. The four-inch, freshwater Ohio shrimp (Macrobrachium ohione) was formerly abundant in the Mississippi River downstream of St. Louis, but began to decline in the 1940s. The species persists today in low but stable numbers along Missouri’s border. Several crayfish species characteristic of the other regions are common in sloughs and marshes on the large river floodplains. These include the White River crawfish (P. acutus) and Cajun dwarf crayfish (C. shufeldtii) along the Mississippi River, and the calico (“papershell”) crayfish (O. immunis) along the Missouri River. The devil crawfish (C. diogenes) is the common burrowing crayfish on floodplains of both rivers.
Content revision: 20090317
