Arkansas River Basin Habitat
This taxon is one of a number of species found in the Arkansas River Basin system. The Arkansas River rises near Leadville, Colorado at an elevation of approximately 3010 meters about thirty kilometers north of Mount Elbert, Colorado's highest peak. Tthe upper reaches of the Arkansas River manifest turbulent high gradient passage through rugged volcanic terrain; the flow continues to the Royal Gorge, where one of the world's highest suspension bridges towers 320 meters above the river surface; thereafter, the river course flows generally eastward through Kansas, thence southeastward through Oklahoma and Arkansas until its discharge to the Mississippi River. The river basin also includes parts of the states of New Mexico, Texas and Missouri. Chief tributaries of the Arkansas River are Purgatoire River, Fountain Creek, Pawnee River, Salt Fork River, Illinois River,Verdigris River, Neosho River, Cimarron River and the Canadian River. The mean annual discharge at Little Rock, Arkansas is approximately 1118 cubic meters per second, a level remarkably undifferentiated from virgin flow, before the era of locks, impoundments and extraction. Water quality at the headwaters near Leadville, Colorado is quite high, consisting of cold, rapidly flowing water of pH 6.3. Concentrations of calcium, sodium, magnesium and chloride are all less than ten milligrams per liter in this pristine headwaters area. Crossing the Southern Plains below Great Bend, Kansas, the pH elevates to a level of 8.0, sodium concentrations rise to a range of 300 to 500 mg/l, with other ions rising by similar large percentages. After receiving the more pristine runoff from the Ozark Plateau, below Fort Smith, Arkansas, the pH level can be measured as low as 7.5, and sodium along with other ion concentrations are reduced by a factor of four. At the Mississippi Embayment, nitrate and phosphate levels are elevated due to row crop agricultural runoff of this region. A number of crayfishes are found in the Arkansas River, including Orconectes palmeri, O. nais, O. virilis, Procambarus acutus and P. simulans. In the downstream reaches of the Mississippi Embayment a number of commercially important native freshwater mussels occur, including the threeridge mussel (Amblema plicata) and mapleleaf mussel (Quadrula quadrula). Other common freshwater mussels found in the Arkansas River and its tributaries are the pink papershell (Potamilus ohiensis), bleufer (P. purpuratus), fawnsfoot (Truncilla donaciformis), fragile papershell (Leptodea fragilis), pondhorn mussel (Uniomerus tetralasmus) and fluted shell mussel (Lasmigona costata). There are 141 species of fish present in the Arkansas River basin, including two near endemics: slough darter (Etheostoma gracile) and speckled darter (Etheostoma stigmae). The federally threatened and near-endemic Neosho madtom (Noturus placidus) occurs in the Neosho River, a tributary that rises in the Flint Hills. Also present in the Neosho River is the endangered Topeka shiner (Notropis topeka). The cardinal shiner (Luxilus cardinalis) is a near-endemic that is now restricted to populations in the Arkansas River and Red River, and disjunctive populations in the Neosho River. In the upper Arkansas River mainstem is found the plains leopard frog (Rana blairi); also occurring in the upper basin are a number of reptiles, including yellow mud turtle (Kinosternon flavescens), midland smooth softshell (Apalone mutica), western spiny softshell turtle (Apalone spinifera hartwegi) and northern water snake (Nerodia sipedon). In the downriver portions of the basin (Eastern Oklahoma and Arkansas) are found the false map turtle (Graptemys pseudogeographica) and the venomous cottonmouth (Agkistrodon piscivorus).