Laserfiche WebLink
1 <br />1 be developed to predict flow conditions necessary for creation and maintenance of the sites (Bliesner <br />and Lamarra 1995; R. Bliesner 1995, pers. comm.). <br />Empirical models of flow- habitat relationships (surface area of specific habitat as a function of <br />flowrate) are being developed to assess flow conditions necessary to optimize specific habitat during <br />specific times of the year. Preliminary relationships indicated that TWA increased with increased <br />' flow (Bliesner and Lamarra 1994, 1995). Also, the area of backwater habitat appeared to be <br />inversely related to flow at low (1,000 - 2,000 cfs) to medium (3,000 - 5,000 cfs) discharges but <br />demonstrated a direct positive relationship as flows increased from medium to high discharges <br />(7,000 cfs). Additional data collection to refine habitat flow relationships is ongoing. Year -to -year <br />variability in the relationship between flow and discrete habitat parameters indicated that the <br />' relationship for some habitat types may be influenced by antecedent conditions. Based on results <br />of additional data collection, it will be determined whether these relationships can be described <br />statistically or mathematically (R. Bliesner 1996, pers. comm.). <br />Ultimately, flow - habitat modeling efforts should provide a meaningful representation of flows <br />required for endangered 4nd native fishes and projections of various types of habitats (e.g., spawning <br />and backwater habitats) that could be provided by different flows. <br />Summary <br />Initial modeling of flow - habitat relationships has been conducted, and additional studies are <br />continuing. This objective will be completed in 1997 as habitat studies are completed. <br />5.2.5. Determine and Monitor Habitat Use of Endangered and Other Native <br />Fishes. <br />5.2.5.1. Determine Habitat Requirements for Different Life Stages <br />Contributing Investigations <br />A number of Program studies provide information on habitat use of native fishes in the San Juan <br />River. Studies by Ryden and Pfeifer (1993, 1994, 1995a, 1995b, 1996a, 1996b) provide habitat <br />information on adult native fish, including Colorado squawfish and razorback sucker. Studies by <br />Miller (1994a, 1995) focus on habitat use of radio- tagged adult Colorado squawfish. Studies <br />providing habitat use information for young Colorado squawfish and other native species were <br />conducted by Platania (1990), Buntjer et al. (1993, 1994), Lashmett (1993, 1994) and Archer et al. <br />' (1995, 1996). Information presented by Propst and Hobbes (1993, 1994, 1995) described habitat use <br />of native species in secondary channel habitats of the San Juan River. <br />Findings <br />Colorado Squawfish <br />Habitat requirements of Colorado squawfish are relatively well known from studies conducted in the <br />upper Colorado River Basin (USFWS 1990). Adult Colorado squawfish (greater than 400 <br />millimeters [mm] in total length [TL]) use several different habitats. During spring runoff, adults <br />San Juan River Recovery Implementation Program December 1997 <br />Summary Report 17 PR -602 -1 <br />