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Show sionally attaining a length of 3 feet, and a weight of 30 pounds. Small streams may harbor suckers, top- minnows, and true minnows; the larger streams may contain, in addition, sunfishes, bonytails, perch, and catfishes, provided there is a zone of aquatic shore vegetation in which such fish spawn, and where their young can hide. Such plants also probably furnish some food. The turbid waters of the principal lowland rivers of the Colorado River Basin either fluctuate so greatly with the seasons, or have such a violent scouring action that such streamside and bottom vegetation is usually sparse or lacking. Artificial reservoirs often completely reverse original stream conditions and may introduce the equivalent of an entirely different " life zone." This will be discussed more fully elsewhere and is mentioned here only to complete the zonal description of the basin. The construction of deep reservoirs like Lake Mead, which discharge large and fairly constant volumes of cold water from which the silt has settled out, has about the same effect as though a section of Transition Zone stream were substituted below the lake for a stretch of the previously barren, hot, and silt- laden river. In this cold stretch of water, trout have been introduced with great success, while in the clear waters of the lake itself, down stream from the silt deposition area, bass thrive, as well as such other introduced species as the bluegill and crappie, and the native warm- water fish previously mentioned. Carp also have been introduced into lower Colorado River waters but are considered undesirable. RECREATIONAL RESOURCES Recreational resources are all natural and cultural features which stimulate, encourage, or provide for the physical, mental, and cultural well- being of the individual. The mountains, with rushing sparkling streams shaded by tall pines in which birds sing; the call of a loon across a lonely lake; the overpowering spectacle of the Grand Canyon; Navajos and their sheep at a water hole in Monument Valley; cowboys riding fence or driving in cattle for the spring round- up; the cry of coyotes across the valley; trout and bass in Lake Mead luring the fishermen to the desert; Hoover Dam; the Figure 14.- Bonita lava flow and Sunset Crater. 17 |