The report discusses the study of habitat use and movement of the rare fishes in the Green River from Jensen to Green River, Utah, in August and September of 1977. The study was conducted to determine the habitat requirements to these rare fishes, primarily young Colorado Squawfish (Ptychocheilus lucius), as evidenced by the habitats they use. The objectives of the study were: (1) determine the physical and chemical parameters of habitats used by all sizes of rare fishes, (2) determine whether spawning occurs in the study area, and if so where the sites are located, (3) determine the movements of the size (age) classes of rare fishes encountered, (4) determine the fish species associated with the study area, and (5) assess the relative importance of various river habitats to the rare fishes.