Laserfiche WebLink
<br />I <br />, <br />il <br />I <br />I <br />., <br />II <br />II <br />II <br />II <br />II' <br />I <br />1 <br />II <br />I <br />II <br />II <br /> <br />'I <br />I <br /> <br />of management activities. <br /> <br />Paramount to identifying the level of recovery possible for the endangered fish <br />species is the characterization of the historic fish populations, including species <br />diversity and abundance. To gain a better understanding of the changes from <br />historic to current conditions, identification of the status and trends of native fish <br />species is necessary. Specific research activities are designed to address the <br />response of the current fish community to various flow regimes. Particular <br />emphasis will be placed upon the response of the native and non-native fish <br />species to various Navajo Reservoir releases. The life history of the endangered <br />fish species will be determined within practical limits. Movement and habitat use <br />patterns, reproductive habits, and young-of-year and juvenile distribution and <br />occurrence will be emphasized. Efforts will be made to determine the response of <br />the endangered fish species, including abundance and distribution, to flow regimes. <br /> <br />While efforts have been made to address fish health concerns in cultural and <br />refugial environments, minimal attention has been given to determining fish health <br />issues in wild populations. Studies of the San Juan River fish community have <br />documented the widespread occurrence of external physical abnormalities. Initial <br />results have indicated that bacterial infections. presumably due to environmental <br />stresses, are adversely affecting fishes. Additional studies will be conducted to <br />determine the identity. extent, and causes of fish health problems in the San Juan <br />River. <br /> <br />Studies are underway to evaluate the genetic distinctiveness of San Juan River <br />populations of Colorado squawfish and razorback sucker. These studies will be <br />incorporated into any decision regarding the necessity for establishment of refugial <br />populations or gene banks. If deemed necessary plans will be developed and <br />implemented to protect the genetic resources of the endangered fish species. The <br />need for an augmentation effort to restore or improve the status of endangered fish <br />species will be determined and implemented. Currently. a captive-bred stock of <br />razorback sucker from the San Juan River Arm of Lake Powell is maintained in a <br />refugia. A portion of these fish are being used in field studies to delineate life <br />history attributes of the species. These data will be used to determine the <br />feasibility, utility, and type of augmentation necessary to assist in recovery of <br />razorback sucker. Similar efforts for Colorado squawfish will be considered and <br />evaluated, without interference with ongoing research activities on the species. <br /> <br />4.4. DETERMINE ROLES OF NON-NATIVE FISH SPECIES IN THE DECLINE <br />OF NATIVE FISH SPECIES AND IMPLEMENT CORRECTIVE ACTIONS <br /> <br />In the Colorado River basin, non-native fish species have been implicated in the <br />decline of the native fish fauna. Past and ongoing studies have indicated that <br />habitat alteration and concurrent or subsequent introduction and establishment of <br />non-native fish species result in depleted native fish populations or their <br /> <br />9 <br />