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Rationale - The rare Colorado River fish are absent from much of their former range. All four species can be easily reared in hatcheries. The stocking of hatchery-reared fish can be used as a tool to re-establish populations in their former range. Considerations - The broodstocks of the rare fish species are small and need to be enlarged to increase the genetic heterogenity. The Green River stock of the Colorado squawfish exhibits a greater migratory tendency than the Colorado River stock. Therefore, it may be desirable to maintain separate broodstocks of this species for different uses. The migratory form could be smocked into long reaches and the nonmigratory form could be stocked into shorter reaches. However, some marked squawfish did not move very far in the Green River indicating that migratory and nonmigratory forms may occur in the same river. Some of these fish were judged to be immature and, therefore, may not migrate during the late spring or early summer when extensive movement occurs that is associated with spawning. Furthermore, large squawfish were collected that were not mature when spawning was occurring, indicating that some fish do not spawn every year. The relation between size at stocking and survival will have to be established since such relations have been demonstrated for other stocked species. This information is important from an economical standpoint. The fish can be stocked at a size where the highest survival is realized without the additional costs of maintaining them in the hatchery. Hatchery stocks could also be used to produce fry for stocking into "grow-out" ponds as described under augmentation of wild stocks above. In addition, spawning channels could be constructed to allow the hatchery broodstocks to spawn naturally and may be important for establishing natural spawning runs. Homing has been established for the squawfish that may be learned or may result from imprinting. A special interagency task group has been organized by the Upper Colorado River Basin Coordinating Committee to estimate the need for hatchery-reared fish and to determine if there is a need for a new hatchery or if existing stations could produce the required production. This group will write a detailed report on the use of hatchery-reared fish in the recovery process. PROTECTION AND ENHANCEMENT OF RARE COLORADO RIVER FISH o Determine the extent of mortality among larval and young of rare fish from irrigation pumps along the Green and lower Colorado Rivers. 14