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" e . J. the Colorado squawfish from the lower Colorado River basin (Nicola 1977) and may threaten its existence in the upper basin as well. LOSS OF STREAM PASSAGE The lower Colorado River basin extends from Lee Ferry, Arizona to the Gulf of California. Existing water development projects have trans- formed this basin into a man-dominated system (Figure 3). The Grand Canyon from the mouth of the Little Colorado River appears to be the only mainstem section not radically altered; however, temperature conditions in the mainstem Colorado River within the canyon is limiting for spawning (Carothers and Minckley 1981). In addition, the drop of 677 m in the 615 km from Lee Ferry to Separation Rapids offers little nursery habitat under present flow regimes (Carothers and Minckley 1981 ) . The Colorado squawfish disappeared from the lower Colorado River basin before its migratory routes were known. Therefore, relating the pres- ence of existing dams in the lower basin to its probable behavior would be conjecture. But migra- tory routes of the Colorado Squawfish in the Green and upper Colorado River sub-basins are under in- vestigation with radiotelemetry and some facts have been gathered. The Green River basin presently contains the greatest abundance of Colorado squawfish in the Colorado River system. Also, the Green River has the least water resource development of the three upper Colorado River sub-basins (Iorns et al.1965). Although the mainstem dam at Flaming Gorge has effectively eliminated the Colorado squawfish with- in its basin and the dam controls discharge from Flaming Gorge to the mouth of the Yampa River, the Yampa River mainstem is not controlled and domi- nates conditions in the Green River below its mouth. Unfortunately, planned development in the upper basin (Figure 4) would dam the Yampaand White River tributaries and a diversion dam on the Green River would obstruct fish passage near the town of Green River, Utah. To date, no provisions have been documented for evaluating the potential for passage of Colorado squawfish through these struc- tures. After the closure of Flaming Gorge Dam, large numbers of Colorado squawfish were observed below the dam attempting to pass upstream (Seet- haler 1978, McDonald and Dotson 1960). It appears this blockage prevented the Colorado squawfish from moving into part of its historic range and the fish presently does not exist above the dam (Tyus et al. 1982a). It is probable that planned developments would result in isolating suitable upstream and downstream habitat from migrating fish and further stress its existence. The discovery of long-distance migration of Colorado squawfish is so recent that no research has been directed toward the feasibility of provid- ing for its passage through dams. Virtually nothing is known about this subject even though it appears that recovery of the species may be dependent upon this kind of information. Pro- visions for such passage would be difficult for the Colorado squawfish since both upstream and e downstream passage appears necessary. To date there is no indication that Colorado squawfish would use conventional passageways and passage of downstream migrants has only been attempted in recent times (Eicher 1970). As important as the provision of passage for adults might be, the passage of young Colorado squawfish and the manipulation of dams to provide proper downstream nursery habitat would be.more difficult. Even if passageway can be provlded through or around impoundments for a~ult and ~oung fish there is a question of reserVOlr operatlon that'is inexorably related to their survival. Can sufficient progress be made in the near future to provide these necessary features? RECOVERY AND RESEARCH NEEDS Recovery of the Colorado squawfish necessi- tates the maintenance of existing populations and reintroduction into part of its historic range where it has be extirpated (Colorado River Fishes Recovery Team 1978). Further studies are ~eeded to determine if Colorado squawfish are obllgate homing species and must return to their ancest~al spawning grounds in order to reproduce. If thlS is proven, the age at which impri~ting occurs must also be determined if reintroductlons are to be successful. If imprinting to the spawning grounds occurs at a very early age, stocking of hatchery reared fish may be undesirable since they m~y not migrate to suitable spawning grounds. ~t mlght be detrimental to existing Colorado squawflsh stocks if hatchery reared fish are placed in competition for food but are unable to successfully reproduce. Perhaps it will be possible to reintro~uce Colorado squawfish eggs or young below dams or.l~ other locations and provide the proper condltlons for the establishment of spawning runs. Unfortunately, no research study has been initiated that addresses these needs to date. Reintroductions of Colorado squawfish into historic range where it has disappeared is fraught with political and technical pro~lems. I~ govern- mental entities agree to such relntroductlons, ex- isting dams may require retrofi~ting with fis~ passage capability, especially lf dam re~ulatlon alone cannot provide the desirable spawnlng and nursery habitat. There is a critical need to pro- vide more behavioral information about Colorado squawfish movement since it unkno~n whether the fish would use various types of flshpassageways if they are provided. CONCLUSION The Colorado squawfish is a very mobile ani- mal that appears to have incorporated long distance spawning migrations and seasonal movement patterns into its life history strategy. The loss of the fish in the lower Colorado River basin has been linked with the extreme modification of that system and loss of fish passage. Proposed projects in the upper basin may result in its extinction or e~tir: pation from the wild. If the Colorado squawflsh lS to be recovered to a non-endangered status, much more information must be obtained about its 141