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0 • <br />Monitoring of the return migrations of these fish would be accomplished at Cross <br />Mountain Canyon using in -situ data loggers at both the downstream entrance and <br />upstream exit of the canyon to record fish movements through this site. Maybell gage <br />records would be used to describe daily flows through the canyon. Daily monitoring of <br />the downstream data logger at Cross Mountain for the first appearance of a radiotagged <br />squawfish could be accomplished by a combination of CDOW and NPS -DNM field <br />personnel on -site. Depending on the effective detection range of the data loggers, <br />directional weirs may be constructed to influence fish movement past the instruments. <br />Use of weirs will involve more intensive on -site maintenance to prevent obstructed flows <br />at the weir. Upstream of Cross Mountain Canyon, movements of radiotagged squawfish <br />would be monitored weekly, then daily when these fish approached within 5 miles of <br />designated passage barriers or limiting reaches during their return migration. <br />Observations would be continuous for fish located immediately below the barriers. Data <br />desired include characterization of fish movements in the immediate vicinity of the <br />barrier (including passage attempts) and the most accurate determination of flow, time <br />and habitat conditions if and when fish pass through the potential barrier. All radiotagged <br />fish would be accounted for if possible during the return migration period. <br />The secondary, or back -up method of evaluating fish passage will be similar to <br />that employed in Masslich (1992) using PIT - tagged adult Colorado squawfish that are <br />captured below the potential passage barriers, and sampling extensively above each <br />barrier to document passage of these marked fish within as narrow a time window as <br />possible. Fish sampling will be largely restricted to pool and deep run habitat during <br />summer and fall, and will be conducted using electrofishing and trammel nets where <br />feasible. Given the low -flow scenario desired for study, frame trap nets, hoop nets, and <br />temporary weirs will also be used where possible. The desired outcome is to capture as <br />many adult Colorado squawfish as possible below Cross Mountain Canyon for <br />identification by previous or newly implanted PIT tags. Tagging records through 1994 <br />for the upper Yampa indicate 137 squawfish have been PIT - tagged with annual recapture <br />rates ranging between 20.4 % in 1993 to 30.0 % in 1995. Given population survival rates <br />of 80 -90 %, mark - recapture populations estimates suggest an adult population of 220 -440 <br />fish in the study area, of which 30 -60 % are PIT - tagged and an additional 60 -300 fish are <br />unmarked. Sampling above the passage sites will be performed 1 -2 times weekly to <br />document recaptures of squawfish identified below each site. This includes RM 98 -105 <br />above the Sweeney diversion; RM 90 -98 above the Maybell canal; and RM 59 -89 above <br />Cross Mountain Canyon. <br />The third back -up method of evaluating passage, in the event options 1 and 2 <br />above cannot be implemented, will be to capture squawfish from above the passage site, <br />implant a radio tag, and relocate them immediately below each site in an attempt to <br />induce the displaced fish to return to its upstream location, through the canyon or <br />diversion structure, during the low -flow condition. It may also be considered for use at <br />the two man -made diversion structures, where the displacement and upstream passage <br />would be less strenuous and more similar to a localized movement effort. Displacing a <br />number of squawfish below Cross Mountain Canyon will be assessed for undesirable <br />risks or impacts and Program approval prior to implementation. <br />2 <br />