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METHODS Movement, Spawning and Rearing Investigations, Colorado and Green Rivers Colorado Sauawfish The movement of adult Colorado squawfish was followed using radiotelemetry. Fish were collected using electrofishing, gill nets, and trammel nets. r Colorado squawfish longer than 450 mm total length (TL) were surgically implanted with radio transmitters following procedures outlined by Tyus (1982). Transmitters used in 1982 had a theoretical battery life of 6 months. In 1983, two transmitter types were used that had LO and 18- month theoretical battery life. River reaches where radiotagged Colorado squawfish were released were searched for the presence of these fish at least biweekly during the July-August spawning season. During the remainder of the year tracking effort varied. A larger area was searched at times when fish could not be located in the immediate study area. The majority of the search effort was conducted using boats; however, airplanes were also employed on occasion. Location and movement of fish was identified by river mile (RM) with the confluence of the Green and Colorado rivers starting as RM 0. Other tributary river mileage was calculated using the tributary mouth as RM 0. Possible spawning areas for Colorado squawfish were identified using radiotelemetered fish, and by analyzing collections of larval fish. The radiotracking effort was intensified during the suspected Colorado squawfish spawning season. When more than one radiotagged fish was found at a particular location -- a possible indication of pre-spawning or spawning activities in that area -- trammel nets were actively fished (drifted) there to determine if other Colorado squawfish might also be present. Captured Colorado squawfish were measured and observations of sexual products and external reproductive characteristics were made. During 3uly, August and September radio tracking efforts were accom- panied by qualitative sampling of the larval fish community. Larval fishes were collected from backwaters and shoreline areas using 0.5-mm- mesh nets. All larval fishes collected were preserved in 5% formaldehyde and identified and counted in the laboratory (Snyder, 1981) . Data on larval fishes collected during each one-week period of the sampling season were pooled within 10-mile reaches. A special Colorado squawfish young-of-the-year (YOY) survey has been conducted each fall in the Colorado River since 1982 and in the Green River since 1980 to identify nursery areas and to deveop an index of annual reproductive success for CS: river regions occupied by YOY = Colorado squawfish of fingerling size (25-b0 mm). These surveys were done with seines (3 and 6-mm-mesh) from September through October when age-0 Colorado squawfish would be 1-2 months old and most often 20-40 mm long. The sampling of YOY was quantitative; the areal extent of each 6