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t IV. IDENTIFICATION OF ENDANGERED FISH STOCKS BASED ON ESTABLISHED CRITERIA Procedures for Reviewing Stock Identification and Characterization. Members of the Program's Biology Committee will annually review presumptive stocks of endangered fishes in the Upper Colorado River Basin as new information becomes available on distribution, behavior, migrations, gene flow (i.e., interchange between stocks), phenotypic information, and genetic information. Even with the available information on criteria for stock identification and characterization, the present ability to evaluate stocks is not complete. Therefore, all stocks will be treated separately (i.e., using a conservative approach) until future information indicates otherwise because all present stocks maybe important in the recovery effort. Revisions to the identified stocks based on new information and changes in this plan will be further reviewed by an ad hoc panel of conservation geneticists. Present Stock Identification and Characterization of Endangered Fishes in the Upper Colorado River Basin. The Program Biology Committee and other interested persons reviewed available information on delineating presumptive stocks of endangered fishes in the upper basin during several meetings in 1993 (Wydoski 1994) and at subsequent Biology Committee meetings. Eleven presumptive stocks of endangered fishes were identified in the upper basin: three stocks of razorback suckers, five stocks of humpback chub, and three stocks of Colorado pikeminnow (Table 1). The identification of the stocks in Table 1 was made conservatively since all stocks maybe important in the recovery effort. Individual bonytail are captured only razely in the upper basin with long periods of time between captures. Therefore, sufficient bonytails aze not available to develop a genetically sound broodstock. Therefore, restoration efforts will be made in the upper basin using bonytail progeny from Lake Mohave origin. f~ V 1 t ~I 1 t 1 i t