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METHODS Rad i o tel eme try The movement of adult Colorado squawfish was followed using radiotele- metry. Fish were collected using electrofishing, gill nets, and trammel nets. Colorado squawfish longer than 500-mm total length (TL) were surgically implanted with radio transmitters following procedures out- ` lined by Tyus (1982). Transmitters used in 1982 had a theoretical battery life of 6 months. In 1983, threetransmitter types were used that had 6, 10, 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 R2i 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 squawf ish 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 drifted through the area 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. Larval and Young-of-the-Year Colorado squawfish Surveys During July, 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) . A special Coior~d.o squawfish young-of-the-year (YOY) survey has been . conducted in the Colorado River since 1982 and in the Green River since 1980 to identify nursery areas and to develop an index of annual repro- ductive success for Colorado squawfish. These surveys were made with 5- mm mesh seines in the Green River and 3 and 6-mm mesh seines in the Colorado River from September through October when age-0 Colorado squawfish would be 1-2 months old and between 25-50 mm Long. The sampling of YOY was quantitative; the areal extent of each seine haul made in 4