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<br />COLORADO RIVER RECOVERY PROGRAM <br />FY 2002 ANNUAL PROJECT REPORT <br /> <br />RECOVERY PROGRAM PROJECT <br />NUMBER: C-6 larval entrainment <br /> <br />1. Proj ect Title: Evaluation of larval razorback sucker drift into flood plain wetlands. <br /> <br />II. Principal Investigators: <br /> <br />Ron Brunson 1 Kevin D. Christopherson <br />Utah Division of Wildlife <br />Northeast Regional Office <br />152 East 100 North <br />Vernal, Utah 84078 <br />435-789-3103/fax: 435-789-8343 <br />e-mail: ronaldbrllnson@lItah.gov <br />kevinc hris to 0 herson@utah.goV <br /> <br />III. Project Summary: <br /> <br />Flood plain wetlands are presumed to be important rearing habitat for the endangered <br />razorback sucker (Wydoski and Wick 1998; Muth et al. 1998; Lentsch et al. 1996). <br />Reproduction by razorback suckers occurs in the spring during peak flows of the hydro graph <br />when highly productive flood plain habitats are accessible (Muth et al. 1998). This seasonal <br />timing of razorback sucker reproduction indicates possible adaptation for utilizing flood plain <br />habitats (Muth et al. 1998). <br /> <br />Based on the assumption that flood plain wetlands provide critical rearing habitat for <br />razorback sucker, the Recovery Program initiated an extensive flood plain habitat restoration <br />program (Levee Removal). The goal of the Levee Removal Program was to restore natural flood <br />plain wetland habitats and functions that support recovery of endangered fish (specifically the <br />razorback sucker; Lentsch et al. 1996). To accomplish this goal, levees at selected wetlands were <br />lowered to increase the frequency of the riverine-flood plain connection to pre-Flaming Gorge <br />Dam levels. In nearly all cases a single breach was cut at the downstream end of selected sites <br />(except Leota L-7). This breach configuration was based on the assumptions that: I) Rates of <br />sediment deposition would be lowest with a downstream breach, resulting in less need for annual <br />excavation to maintain connections between the site and the river; and 2) Downstream breaches <br />would be less risky in terms of affecting site morphology and main channel stability, and would <br />be less likely than an upstream breach to reroute the main channel or convert the wetland into a <br />secondary channel. However, the primary problem with downstream configuration oflevee <br />breaches is that transport of drifting larvae to the flood plain is not maximized. This is <br />significant because flood plain wetlands are occupied by high densities of nonnative fish and <br />other potential predators. Optimization of larval entrainment in the flood plain may be crucial <br />for ensuring some survival of entrained larval razorback sucker. Sites with single downstream <br />breaches do not optimize larval entrainment because fish can only be entrained on days of <br />increasing flow. <br /> <br />(-6 larval entrainment page 1 <br />