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unusual fishes of the Colorado River that are found nowhere else in the world. The continued existence of these rare fishes will require the cooperation of diverse interest groups, as well as improved communi- cation between persons of diverse fields of knowledge and expertise. All future development will not grind to a halt because of such unusual fishes as the squawfish and the humpback chub, as claimed by some alarmists. Some delay, compromises, and modifications in future projects may be necessary, however, to maintain cer- tain environmental conditions and avoid the extinction of the rare fishes. Concerned citizens are urged to assist in gather- ing information on the fishes discussed in this bul- letin. The areas involved cover vast expanses of habitat. Scientific collecting gear has not been highly effective in capturing fishes such as squaw- fish, razorback suckers, and bonytail and humpback chubs. Fishermen catching any of these endangered or threatened species must, according to the law, release them unharmed; however, a report of the catch, giving size of fish and location and date of capture should be made to a local District Wildlife Manager or to a regional office of the State Division of Wild- life. Squawfish and humpback chubs are being tagged as part of current research projects. If a tagged fish is caught, the tag number should be included in the report of the catch. Such information may pro- vide new distribution records for a species or may lead to the discovery of a species such as the bony- tail chub -- now believed extinct in Colorado. The native fishes of the Colorado River basin received little attention until recent times. The area involved is large and the physical, chemical, and biological interactions affecting the well-being of the native fishes are complex. Thus, detailed data and documentation on cause and effect relation- ships to explain the decline of rare fishes are largely lacking. The assessments we make here on the basis of available information, must be considered in the realm of speculation. 1982 UPDATE Since this bulletin was written in the summer of 1980 a considerable amount of new information has been obtained. The U.S. Fish and Wildlife Service's Colorado River Fishery Project completed three years of studies on endangered species and issued its final reports in 1982. This work will be continued until 1985 as the Colorado River Fishery Monitoring Program to refine and verify aspects of the earlier study. The Colorado Division of Wildlife's endangered species monitoring and larval fish sampling program was con- tinued in 1981 and 1982. The use of minute radio transmitters implanted in specimens of squawfish, humpback chub, and razorback sucker, allowed for the tracking of movement which confirmed that the squaw- fish is a highly mobile species, capable of utilizing 200 miles or more of river during an annual cycle. The Endangered Species Act was reauthorized and amended in October, 1982. At the end of each section we incorporate a syn- thesis of the new information updated to December, 1982. 4