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METHODS Movement, Spawning and Rearing Investigations The movement of adult Colorado squawfish was followed using radiotelemetry. Fish were collected using electrofishing, gill nets, trammel nets, and traps. Colorado squawfish longer than 500 mm total length (TL) were surgically implanted with radio transmitters following procedures outlined by Tyus (1982). Transmitters weighed about 10-11 grams in air and had a life expectancy of approximately 6 months. All rare fishes collected were weighed (grams) and measured (TL, mm). River reaches where radio-equipped Colorado squawfish were released were searched for the presence of these radiotagged fish at least bi- weekly. 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 and helicopters were also employed. 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 analysing collections of larval fish. The radio tracking effort was intensified during the suspected Colorado squawfish spawning season (July-August). When more than one radio-equipped fish were 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 be present. Collected Colorado squawfish were measured in the usual manner, and observations were made for sexual products and any external reproductive characteristics of the fish. During July and August radio tracking efforts were accompanied by qualitative sampling of the larval fish community. Larval fishes were collected from backwaters and shoreline areas at 2-5 river mile intervals, using fine-mesh hand nets. All larval fishes collected were preserved in formaldehyde and sent to the Larval Fishes Laboratory, Colorado State University, Fort Collins, for identification. A special Colorado squawfish young-of-the-year (YOY) survey was conducted each fall to identify nursery areas, river regions occupied by • YOY Colorado squawfish of fingerling size (25-60 mm). These surveys were done with seines (3x5 mm-mesh) from mid-September through October. The YOY surveys were quantitative; the areal extent of each seining a effort was recorded, as were the water depth, water velocity, and substrate characteristics of the areas sampled (Archer et al. 1980). Sampling sites were river backwaters selected at about 5 mile intervals. At least two seine hauls were made in each backwater, and one similar haul was made along the adjacent river shoreline. -4-