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<br />Mr. Calvin Joyner <br /> <br />c:) sucker are currently experiencing in the San Juan and other subbasins <br />~ throughout the Upper Basin. <br />e::> <br />~~ Water aualitv <br />CJ1 <br />~ Surface and ground water quality in the Animas, La Plata, Mancos, and San Juan <br />River drainages have become significant concerns (Brogden et al. 1979). <br />Potential heavy metal and/or selenium contamination in project-affected rivers <br />and newly created reservoirs and the subsequent bioaccumulation in the food <br />chain could become a problem for the predatory Colorado sQuawfish, as well as <br />the razorback sucker. <br /> <br />6 <br /> <br />Changes in water Quality and contamination of associated biota are known to <br />occur in similar Bureau projects in the San Juan drainage (i.e., irrigated <br />lands on the Pine and Mancos Rivers) where return flows from irrigation make <br />up a portion of the river flow or other aquatic sites downstream (Sylvester <br />et al, 1988). Increased loading of the San Juan River and its tributaries <br />with soil salts, elemental contaminants, and pesticides from irrigation return <br />flows could potentially degrade water quality and cause harm to the endangered <br />fishes. <br /> <br />Turbiditv <br /> <br />Very little information is available on the influence of turbidity on the <br />endangered Colorado River fishes. It is assumed, however, that turbidity is <br />important, particularly as it affects the interaction between introduced <br />fishes and the endemic Colorado River fishes, Because these endemic fishes <br />have evolved under natural conditions of high turbidity, it is concluded that <br />the retention of these highly turbid conditions is an important factor for <br />these endangered fishes. Reduction of turbidity may enable introduced species <br />to gain a competitive edge which could further contribute to the decline of <br />the endangered Colorado River fishes. <br /> <br />Colorado Sauawfish <br /> <br />Historical and Current Distribution <br /> <br />The Colorado squawfish evolved as the main predator in the Colorado River <br />and San Juan River systems. The diet of Colorado squawfish longer than <br />3 or 4 inches consists almost entirely of other fishes (Vanicek and Kramer <br />1969), The Colorado squawfish is the largest cyprinid fish (minnow family) <br />native to North America and, during predevelopment times, may have grown as <br />large as 6 feet in length and weighed nearly 100 pounds (Behnke and Benson <br />1983). These large fish may have been 25-50 years of age. The Colorado <br />squawfish currently occupies about 1,030 river miles in the Colorado River <br />system (25 percent of its original range) and is presently found only in the <br />San Juan and other subbasins above Glen Canyon Dam. <br /> <br />Based on early fish collection records, archaeological finds, and other <br />observations, the Colorado sQuawfish was once found throughout warmwater <br />reaches of the entire Colorado River Basin, including reaches of the upper San <br />Juan River and possibly its major tributaries. Colorado sQuawfish were <br />