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Indices of imp?xliment to passage include aggregation of Colorado squawfish in <br />habitats immediately below the canyon in the large pool that exists there, or in available <br />pool habitat or other habitats providing cover (deep runs) within 0.5 miles below the <br />diversion structures. Another index would be evidence of delayed passage until fall when <br />flow level increases. Successful passage would be evident from recapture of tagged fish <br />upstream of each potential barrier in a time frame that indicated likely passage during the <br />threshold low -flow condition. Since passage by squawfish through these potential <br />barriers has occurred historically, recapture data will likely refine the low flow range at <br />which return spawning migrants will move through each site. <br />Objective 4. <br />If one or more of the three potential barriers is documented as impeding passage <br />of Colorado squawfish through the Objective 2 assessment or Objective 3 results, the <br />adverse implications of the impedance will be extrapolated as an effect on population <br />survival, annual larval production, recruitment, or growth, and analyzed via the <br />population dynamics model (Crowl) for long term effect on the Yampa River population <br />abundance. Presuming at this time that one or more of these population parameters will <br />be negatively impacted, the overall influence of passage problems on persistence of the <br />Yampa River population and its subsequent influence on recovery efforts for the species <br />would also be described. It is difficult at this time to predict what a significant level of <br />passage impact would be necessary to affect the Yampa squawfish population, and how <br />this adverse impact would be manifested as a population dynamic <br />VII. Task Description and Schedule: <br />Tasks described under Objectives 1 and 2 will be accomplished by the team identified in <br />Approach for Objective 1. CDOW will assume the lead for biological components of <br />analyses with FWS assistance. CRWCD and contractors will assume the lead for <br />hydraulic modeling and hydrologic analyses. <br />Objective 1. <br />Task 1: October through December 1995 <br />Conduct review of existing aerial photographs, previous work, general knowledge <br />of the Yampa River to finalize selection of up to three natural "limiting reaches" <br />for further study. <br />Task 2: October through December 1995 <br />Review existing information such as mapping, previously constructed hydraulic <br />models, etc. for the selected reaches. <br />7 <br />