WSP12210 - Laserfiche WebLink

Home Browse Search

. . 2 winter period including the months of December through March or April, and the spring period which includes the period when the Yampa River is at spring runoff stage. We are providing comments on each of the recommendations and the available data on which the recommendations were based. LATE SmmEll AND FALL - PROTECTION OF RURSEIlY HABITAT AND YOUNG OF THE YEAR The recommendation for late summer and fall was provided as flows necessary for ensuring that nursery habitat is protected and not adversely affected by daily fluctuation or excessively high releases fro. the dam. The recommendation is given as a target flow of 1800 cfs plus or minus 25 percent (range from 1300 t62300 cfs). This recommendation was based on approximately 7 years of young of the year fish collection and growth information correlated with annusl flow events. These data were also compared with aerial photography work performed by our remote sensing staff in Denver. Except for so.e modification in the actual target flow resulting fro. revision of the historic flow measurements by the United States Geological Survey (USGS), we support the target flow recommendation. The information presented for maintaining s flow regime that would increase available backwater habitat and therefore potentially increase the survivability of young native fish during the nursery period appears conclusive. We agree protection of each reproductive.year class .is one of the important measures necessary for . ... ....., . ..recovery of. the Co1.oractO..squaWf1.sh.snd:.pcilislblyothernat1.ve 1!pecies including ....... :.. . the razorback sucker. . WINTER FLOW RECO!lMENDATION - PROTECTION OF ADULT AND YOUNG FISH HABITAT The reco.mendation for the winter period for adult Colorado squawfish and razorback sucker was based on the contracted study performed by Dr. Richard Valdez and W. M. !lassl1ch at Bio/West, Inc. in Logan. While we concur with the basic results of the study, i.e., flow events can cause adult fish to move, adverse effects of the movement were not demonstrated. We recognize that it was not within the scope of the winter habitat investigation to determine the effects of long distance winter movement on adult squawfish and razorback sucker. We also know that this was the first definitive information concerning adult fish winter behavior; however, we believe there is insufficient information available in the report on which to base a specific flow recommendation. Thus, it is our opinion that more information should be collected similar to the fluctuating test flows (other hydrologic conditions) tested during the second year effort of the study and discussed in"the final "Winter Habitat Report." In addition, the information presented for over winter survival of young of the year fish was limited snd little information was presented on winter flow needs of early juvenile life stages. Concerns regarding young of the year and juvenile survival during the winter and runoff period have been raised by researchers conducting investigations on the Yampa and mainstem Colorsdo Rivers. We believe that a flow recommendation for the winter period should include the maintenance of all or as many life stages as possible. In that the recommendation given in the consolidated report does not place much emphasis on young of the year or juvenile life stages and does not adequately address the adverse effects of fluctuating flows on adult fish, we believe the recommendation should be further evaluated.