8289 - Laserfiche WebLink

Home Browse Search

DRAFTvi EXECUTIVE SUMMARY The nursery habitat study was conducted from 1992 to 1996 under the auspices of the Recovery Implementation Program, to further define Colo o s uawfish use ofihabitat. The relationships between peak and sampling_flows, habitat availabilit~r tem e~rahue, Colorado .._. squawfisli .~~ch and growth rates and density of sympatnc non-nat~ve..cyps~.~ds were examined. Colorado squawfish prefer backwater habitats that are formed behind large sandbars from scour channels, and are larger, deeper and more persistent than other habitats. Non-native cyprinids also preferred this habitat. All types of habitat including quality habitat increased in quantity during low water years, and decreased in high water years. There were slight decreases associated with higher samplingsflows. Non-native cyprinids were positively correlated with increased habitat availability, while Colorado squawfish were negatively correlated. Total degree day accumulation was higher in low water years, which in turn was positively correlated with high growth rates for squawfish, and with high overwinter survival rates. The density ofnon-native cyprinids was negatively correlated with Colorado squawfish catch rates. Colorado squawfish are limited more b the resence ofnon-native rinids than by habitat availability in the lower ~Rixex. We recommend managing the river system for a variety of flow scenarios to emulate the natural hydrograph. The ISMP sampling protocol is sufficiently representative of Colorado squawfish annual trends. We recommend no changes.