7810 - Laserfiche WebLink

Home Browse Search

PURPOSE AND NEED The purpose of this environmental assessment is to select an acceptable procedure for disposal of surplus captive-reared endangered fish. A need has been identified for the development of captive broodstocks of endangered Colorado River fishes that are genetically similar to the wild endangered fish stock that was used as founders. Captive broodstocks serve as an "insurance policy" if the wild stocks become extirpated and provide fish for experimental studies that are part of recovery efforts . Since attrition rates are not known in captive propagation of the endangered Colorado River fishes, more fish are produced than are needed in the recovery effort to compensate for high attrition rates. Many propagation activities may produce more fish than are needed to meet specified requirements. This additional production allows the hatchery manager to compensate for unknown or unpredictable attrition rates to ensure that specified requirements are met. Planned captive propagation minimizes the production of endangered fish that will be excess to Program needs. However, fish that are surplus to actual need become a liability to the Recovery Program because they require valuable resources (e.g., people, facilities, and funds). Therefore, Recovery Program participants developed "Guidelines for the Disposition of Captive-Reared Endangered Fish" (Guidelines) to address this issue. This Environmental Assessment compares several alternatives that could be used in the disposition of captive-reared endangered fish, including the Guidelines, and discusses the potential impacts of each alternative. BACKGROUND Water development in the Upper Colorado River Basin has resulted in changes in the historic water regime of this important river system that, in turn, has affected water temperatures and habitat such as backwaters and flooded bottomlands that were apparently crucial to successive recruitment of the endangered fishes. Construction of dams in the upper basin also blocked natural migrations of endemic fishes. Subsequently, non-native fishes were introduced, either intentionally or accidentally, that have become established in the river and are suspected to be competitors with, or predators on, the native fishes in this unique river system. These changes have resulted in the razorback sucker (Xvrauchen texanus), bonytail (Gila ele ans), humpback chub (Gila c ha), and Colorado squawfish (Ptychocheilus lucius) being listed as "endangered" under the Endangered Species Act of 1973, as amended. These endemic fishes once played a positive and important role in the lives of Upper Colorado River Basin residents by providing sport fishing opportunities and food (Quartarone 1993). Although spawning has been documented and larvae or juveniles of some of the endangered fishes have been collected in the upper basin, the primary limiting factor is poor survival in the early life stages that results in inadequate recruitment to maintain self-sustaining wild stocks.