North Platte River Fish Survey Casper to the Nebraska State Line

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North Platte River Fish Survey - March 1999 INTRODUCTION Page 1 The States of Nebraska, Wyoming, and Colorado and the U.S. Department of the Interior (DOI) have signed a Cooperative Agreement which guides the activities of the Platte River Endangered Species Partnership. This partnership is designed to improve and conserve habitat for four threatened and endangered species that use the Platte River in Nebraska. The State of Wyoming's contribution to this effort is the proposed Pathfinder Modification Project. In support of this effort, the U.S. Bureau of Reclamation (Reclamation) conducted an extensive fish survey of the North Platte River from Casper to the Nebraska State line to supplement the Wyoming Game and Fish Department's database for fish communities that may be impacted by this proposed project. The proposed Pathfinder Modification Project would increase the capacity of the existing Pathfinder Reservoir by 21,649 ha to recapture storage space lost to sediment deposition behind the dam. The existing spillway would be raised approximately 0.73 in with the installation of an inflatable bladder system attached to the spillway. Another option being considered is modifying the operations of the North Platte River Reservoir System which may eliminate or reduce the need for construction of the bladder system. Both the physical structure and modification to operations will be analyzed in the environmental impact statement process being conducted by DOI. The North Platte River system supports an important sport fishery for the State of Wyoming, and provides habitat for native fish species. Changes in operations of the reservoir system may affect both native and sport fish either positively or negatively. Critical to understanding the potential effects are current data on fish communities throughout the North Platte River. The Wyoming Game and Fish Department (WGFD) has adequate long -term data on fish populations and the sport fishery for the North Platte River from Casper upstream to the headwaters. However, recenE data are lacking for the river from Casper downstream to the Wyoming/Nebraska State line, with the exception of Glendo Reservoir. This extensive section of the lower river supplies an important component of overall fish habitat of the North Platte River. Fish can be one of the most sensitive indicators of aquatic ecosystem quality and can reliably reflect conditions that are suitable or unsuitable for their existence (Yoder and Smith 1999). Reclamation was requested by fisheries biologists with the WGFD to focus efforts on the native fish community for which little current information exists. STUDY AREA We surveyed fish in the North Platte River from the E. K. Wilkens State Park about 13 km east of Casper, Wyoming, downstream to the Nebraska State line (Figure 1). Maps of each study site are included in the Results section. For study purposes, the river is divided into five reaches: Casper to Douglas; Douglas to the inlet of Glendo Reservoir; Glendo Dam outlet to the inlet of Introduction /Study Area