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<br />0 <br />1.-:"'1 <br />(..,) <br />'. ., <br />c.o B. <br />.0 <br /> <br />10 <br />EXPERIMENTAL STOCKINCJ OF eOLORAOO SaUAWFISH IN THE SAN JUAN ~IVE~ <br /> <br />The preferred altemative involves a 2-year effort of stocking and monitoring in 1996 and <br />1997. Approximately 100,000 Age-1 sized Colorado squawfish (70-90 mm) will be obtained <br />the first year from Dexter National Fish Hatchery in Dexter, New Mexico, and experimentally <br />stocked to determine the overwinter survival of stocked Colorado squawfish at this size during <br />an expected low flow winter. Monitoring these fish will also aid in the determination of what <br />habitats are utilized by Colorado squawfish of this size. An equal number of Age-O sized <br />Colorado squawfish (20-40 mm) will be stocked in 1997. The objectives of the 1997 <br />stocking efforts are to determine if the quality and quantity of low-velocity habitats in the San <br />Juan River are sufficient to support retention and recruitment of young-of-year Colorado <br />squaw fish, and to determine the effects of diversion canals on young-of-year Colorado <br />squawfish movement and survival. <br /> <br />In late October/early November, it its proposed that 100,000 juvenile Colorado squawfish <br />obtained from Dexter National Fish Hatchery will be stocked into the San Juan River. The <br />otoliths of these fish have been marked with a tetracycline hydrochloride (Tel stain. Half <br />(50,000) of these fish will be stocked into the upper San Juan River (Mixer Reach RM 131- <br />126) and the remaining half into the lower San Juan (John's Canyon RM 25-201. These <br />reaches were chosen for two reasons: 1) the upper reach is iust below the only known <br />spawning bar in the San Juan River and has a high concentration of nursery habitats and 2) <br />the lower reach is low-gradient, has a high concentration of nursery habitat, and is proximal <br />to locations where the highest concentration of wild larval Colorado squawfish have been <br />caught (19 of 21 have been captured below RM 13). The 2 lots of 50,000 fish will be spray <br />marked to allow field researchers to differentiate between the two stocking groups. The spray <br />mark should last into the spring/summer of 1997. After that period, captured fish will be <br />sacrificed to differentiate between stocked and wild specimens via the TC otolith markings. <br />Tetracycline hydrochloride is a water soluble fluorescent chemical that becomes incorporated <br />into otoliths of marked fish. The captured fish must be killed in order to obtain the otoliths <br />and determine the markings. Objective NO.8 of the proposed action will use informatioQ from <br />field collections as well as a lab component to determine the retention time of the spray mark. <br />The lab component will hold asampJe of spray marked fish in captivity to determine retention <br />times for the spray marks and, thus, their feasibility for use in non-lethal monitoring efforts. <br /> <br />One week following the October/November stocking, a representation of al/ habitats, including <br />low-velocity habitats will be sampled throughout the two stocked reaches. This initi"al <br />sampling will determine what habitats are being used and the movements of the'stocked fish. <br />The 2 reaches will then be sampled 1 month following the stocking. Sampling will then be <br />coordinated with the regularly schedule Utah Division of Wildlife Resources nursery habitat <br />trips -- late March/early April to determine overwinter survival; late August to intensively <br />sample low-velocity habitats; and September to characterize fish communities in low-velocity <br />habitats and prior to winter stresses). <br /> <br />In August 1997, 100,000 young-of-year (Age 0) Colorado squawfish will be obtained from <br />Dexter National Fish Hatchery and Technology Center. A unique TC stain and/or chemical <br />spray mark will be used to batch mark five groups of 20,000 fish within the first week after <br />swim-up. These marks will allow the icfentification of fish from individual stocking events. <br />The fish will be stocked at an average of 20-40 mm total length approximately 1 kilometer <br />