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<br />this species in the Upper Colorado River Basin (Tyus 1984; Burdick and <br />Kaeding 1990). Although the actual role that blockage might have <br />contributed in the decline of these species in the upper basin is <br />unknown, providing fish passage past instream barriers has come to be <br />considered an important means to aid the recovery .of this species. <br /> <br />The Redlands Diversion Dam. constructed in 1918, is a 12-foot high <br />irrigation structure that has effectively restricted upstream movement <br />of fishes from the Colorado and lower Gunnison rivers to the upper <br />Gunnison River. The Gunnison River upstream of the Redlands Diversion <br />Dam is historic habitat for both Colorado squawfish and razorback <br />sucker. A small enclave population of juvenile and adult Colorado <br />squawfish presently exists upstream of Redlands. The last documented <br />capture of a wild razorback sucker in the Gunnison River upstream of <br />Redlands.Diversion Dam was in 1981 (Holden et al. 1981). Twenty-one <br />adult razorback sucker were stocked in April 1994 and another four <br />adults were stocked in the fall of 1995. Three-hundred sixteen <br />juvenile razorback sucker were stocked October 1995 and 287. 9 to 16- <br />inch sub-adult razorback sucker were stocked in October 1996. In 1997, <br />a total of 3,732. 5- to 15-inch juvenile and sub-adult razorback sucker <br />was stocked in the Gunnison River at river mile 57 on nine different <br />dates from three different sources between 12 September and 14 October. <br /> <br />Hypothetically, reduction of the historical population of Colorado <br />squawfish in the river reach upstream of Redlands Diversion Dam may be <br />explained by instream barriers that have served to effectively block <br />adult fish during seasonal movements. especially spawning migrations. <br />If spawning occurred downstream of Redlands Diversion Dam. :the upstream <br />stock would have been rapidly depleted of adults migrating ,downstream <br />and over the diversion dam to spawn. On the other hand. if spawning <br />occurred upstream of Redlands Diversion Dam. larval drift would likely <br />place young-of-the-year fish downstream of the diversion dam and <br />effectively block recruitment to the adult population. Over time. the <br />upstream populations would diminish through attrition of adults and <br />lack of recruitment. <br /> <br />The capture of larval Colorado squawfish in 1995 and 1996 1ndicates <br />that Colorado squawfish spawn in the Gunnison River upstream of <br />Redlands Diversion Dam. possibly as far upstream as Bridgeport (RM <br />29.3). Larval Colorado squawfish have been collected up- and <br />downstream of the Redlands Diversion Dam. One larval Colorado <br />squawfish was collected immed.iately downstream of. the Redlands <br />Diversion Dam in August 1986 (Osmundson and Kaeding 1989). Two other <br /> <br />Redlands 2 <br />