Historical Changes in Large River Fish Assemblages of the Americas
Historic Changes in the Rio Grande Fish Fauna: Status, Threats, and Management of Native Species
Bob Calamusso, John N. Rinne, and Robert J. Edwards
Abstract.—The Rio Grande is the fourth longest river in North America and the 22nd longest in the world. It begins as a cold headwater stream in Colorado, flows through New Mexico and Texas, where it becomes warm and turbid and finally empties into the Gulf of Mexico. The diversity of native fishes is high in the Rio Grande ranging from freshwater salmonids in its upper reaches to coastal forms in the lower reaches. Historically, about 40 primary freshwater species inhabited the waters of the Rio Grande. Like many rivers throughout North America, the native fish fauna of this river has been irrevocably altered. Species once present are now extinct, others are threatened or endangered, and the majority of the remaining native fishes are declining in both range and numbers. Today, 17 of the 40 primary native freshwater fishes have been either extirpated in part or throughout the Rio Grande drainage. This chapter examines the river, its fauna, and its current plight.