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<:;:) . ,.-:) c'~ ;.",.' 0) 7 lrol.~::. the four-month low flow test period. Systematic biological monitoring of stocked fish would be conducted to obtain biological information from the experimental effort. Habitats used would be characterized by radio telemetry. Recaptured fish would provide information on survival, movement, post - stocKing dispersal, age and growth, and whether stocked fish are interacting with wild razorback sucker. Any wild razorback sucker captured would be weighed, measured, checked for general health, tissue-plugged for genetic analyses, and surgically implanted with a radio transmitter. C. PROPOSED AREA The San Juan River and its tributaries form the second largest of the three sub-basins comprising the Upper Colorado River Basin. The San Juan River drains about 38,000 square miles of southwestern Colorado, northeastern Arizona, northwestern New Mexico, and southeastern Utah. From its origins in the San Juan Mountains of Colorado, the San Juan River flows some 31 miles to the New Mexico border, 190 miles westward to the Four Corners area, and thence another 136 miles to Lake Powell. In its upper reaches, the river traverses rugged terrain and has a. relatively high gradient. The river emerges from canyon-bound reaches shortly after entering New Mexico and flows through a broad floodplain for much of its course in New Mexico and Utah. About 70 miles upstream of Lake Powell, the river again enters canyon reaches for the remainder of its course. The river is generally restricted to a single channel in canyon portions, but is often divided into several channels in floodplain reaches. The San Juan River has comparatively few perennial tributaries, most of which are in upper reaches. Historically, the Pinos, Piedra, Navajo, Animas, La Plata, and Mancos rivers, Rio Blanco, and McElmo Creek were the only perennially flowing tributaries. Other streams such as Montezuma and Chinle creeks seasonally contributed flows. Numerous washes and arroyos also entered the river, but none provided regular flow. Among tributaries, the Animas River contributed the greatest flow. The three stocking sites originally selected for the stocking effort were chosen based on a high occurrence of nearby backwater or secondary channel habitat, and characteristics knoWn or suspected to be highly important to the survival of the species. The three sites were Kept approximately 25-30 miles apart, so that future monitoring efforts could easily detect any distinctive movement patterns or downstream displacement of stocked fish. Stocking sites are located at river mile 136.6 (Mixer Site, New Mexico), river mile 117.5 (Upper Utah Site), and river mile 79.6 (Bluff, Utah Site). These sites were modified from the original stocking plan for access purposes. A fourth site was added in October 1994 at RM 158.6. The Bluff Site was selected because this area has accounted for the only documented razorback sucker captures in the main stem San Juan River. The Mixer Site has a