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Reasons for Decline To understand the problems facing the Colorado squawfish, it is necessary to envision what the Colorado River itself was once like. Waters (1946) calls it an outlaw, savage and unpredictable of mood, known at last simply by its one unchanging color, Rio Colorado, the great Red River of the West. Seventeen hundred miles (2,700 km) long, it is cliff-bound nine-tenths of the way. In its journey to the Gulf of California, it drops over two miles (3.2 km), creating some of the most turbulent waters found on earth. Its volume is unpredict- able. It can crawl past Yuma, Arizona at a mere 3,000 cubic feet per second (5100 cubic meters per minute) or roar by during the spring flood at 380,000 cubic feet per second (645,000 cubic meters per minute). It often seems more solid than fluid; it is high in mineral salts-carbo- nates, sulfates and chlorides of calcium, sodium and magnesium. In fact, it is so high in salts that it was long questioned whether it could safely be used for. drinking water or even irrigation. And few rivers are so choked with silt. Averaging 0.62 silt content by volume, it formerly carried over 100,000 acre-feet of mountain and desert to the Gulf of California each year, forming the delta Aldo Leopold so beautifully described in "A Sand County Almanac." Indeed, at one time the Colorado River was a harsh environment for any living thing, and the fish that evolved in its muddy, turbulent waters are unique. Some fornied strangely modified backs, e.g., humpback chub (Gila ~) and razorback sucker (Xyrauchen texanus); while others developed thin caudal peduncles, tiny scales and large, falcate fins, e.g., bonytail chub (Gila elegans); unique adaptations to a demanding environment. And sitting on top of the trophic pyramid, the top carni- vore of the Colorado system, was the squawfish. Adapted to survive in this strange world of humpbacked fish and dynamic environmental con- ditions, he preyed at will. on those other fishes, themselves so uniquely adapted to the. Colorado River. With the danming of the river by Hoover Dam in 1935 and then with over 20 other mainstream and tributary dams, the river's character has changed. Over much of its course, it has beccane a series of mill ponds, connected by clear, oold trout streams. Is it any wonder that those species, adapted to the Rio Colorado, find themselves strangely out of place in this newly created, man-made environment? At present it seems most reasonable to relate declining squawfish num- bers and range to several causes. A number of investigators believe squawfish have become extinct in the lower basin and declined drasti- cally in the upper basin because of mainstream dams and their resultant changes on the rivers. Above the-dams the newly ponded waters apparent- ly are so foreign to Colorado squawfish that no population build-up has ever been recorded. The few individuals caught in Lake Powell (Utah) are thought to come from the riverine portion above the lake. Elimination of squawfish from these reservoirs appears to be more 6 t t 1 1 t 1