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14 Utah, Uintah and Grand Counties. The Green River (Desolation and Gray Canyons) from Sumner's Amphitheater in T. 12 S., R. 18 E., section 5 (Salt Lake Meridian) to Swasey's Rapid (river mile 12) in T. 20 S., R. 16 E., section 3 (Salt Lake Meridian). Utah. Grand County: and Colorado. Mesa County. The Colorado River from Black Rocks (river mile 137) in T. 10 S., R. 104 W., section 25 (6th Principal Meridian) to Fish Ford in T. 21 S., R. 24 E., section 35 (Salt Lake Meridian). Utah. Garfield and San Juan Counties. The Colorado River from Brown Betty Rapid in T. 30 S., R. 18 E., section 34 (Salt Lake Meridian) to Imperial Canyon in T. 31 S., R. 17 E., section 28 (Salt Lake Meridian). IMPORTANCE OF THE 15-MILE REACH This section includes a summary of a draft Service r_ea'or_t titled "Importance ~~ of the 15-Mile Reach to Colorado River Populations of Endangered Fish" ~ ._~ (Osmundson 1996. The report is hereby incorporated into this biological ,~.~~ s~ pinion. ~.F:,~•s~,~co~~~~~~..Lf~~ ~~- The Colorado squawfish requires a variety of specific habitat types~to~ulfi'~1 r~c~--~. ~ its life history needs. Some of these required habitats are found only in ~Q,, certain areas of the river and are separated from other required habitats by ~,f~" long distances. The 15-mile reach provides important spawning habitat for ~~ Colorado squawfish; Colorado squawfish spawning was documented within the 15-mile reach in 1982 and in 1995 by the capture of larval Colorado squawfish. The cleaner cobble bars found in upstream reaches, such as the 15-mile reach,l provide the most suitable sites for Colorado squawfish spawning. The larvae /~ hatched from eggs deposited in these upstream reaches drift downstream with J ~` the current. In downstream reaches, primarily below Moab, Utah, deposits of ~-: silt and sand provide many warm backwater sites where young Colorado squawfish feed upon the abundant zooplankton and chironomid larvae. When they become piscivorous, young Colorado squawfish feed upon the abundant small fishes found in these areas. As Colorado squawfish become larger and approach adulthood, they require larger forage fish to maintain growth rates. However, larger forage fish are scarce in these downstream reaches and maturing Colorado squawfish begin to move up and-down the river seeking better feeding grounds. Eventually, adult Colorado squawfish discover the abundant supplies of native fish in the upper river including the 15-mile reach and remain in these upper reaches for the remainder of their lives. Forage fish are generally more abundant in these upper reaches because food for these fishes, algae and aquatic insects, is more abundant. Algae, phytoplankton (free-floating algae) and periphyton (algae that grows on rock surfaces), is more abundant because the higher water clarity allows deeper light penetration necessary for its growth. Aquatic insects are more abundant because the swifter currents resulting from generally higher gradients flush gravel and cobble substrates providing silt-free crevices required by many aquatic insects. Because of the increasing abundance of forage fish as one moves up river, the average size of