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~~ described from a series of depth, velocity and substrate measurements. Bottom substrates are classified according the following scheme: Silt f ine gritty material Sand less than 3 mm diameter Gravel 3 mm to 76 mm Rubble 76 mm to 305 mm Boulder 305 mm and larger Bedrock rock outcropping The 4.5 mile reach between intensive survey sites was sampled in a more general manner, primarily by electrofishing, in order to provide a survey of adult fishes. Physical data were collected only at sites of rare fish captures. Each habitat present in the intensive reaches was sampled with every effective gear type. Rare fish captures were located on river maps to the nearest 0.1 mile (1.6 km) and water depth, velocity measure- ments and the predominent substrate type recorded. All fish collections were accompanied with detailed information regarding location, date, time of day, measure of effort, habitat type, substrate type, and a series of depth and velocity measurements. Fish larger than 100 mm total length (TL) were weighed and measured individually. Large samples of smaller fish were sorted into 10 mm groups and counted. Stomachs were removed from the rare fish that succumbed and the rest of the carcass preserved for later examinations. All rare fishes greater than 200 mm TL were tagged with a Carlin dangler tag attached through the dorsal musculature immediately below the posterior 1/3 of the dorsal fin. Sampling Equipment The effectiveness of electroshocking equipment is diminished substantially by high conductivities, great depths and high turbidities encountered in the Green River. However, a Coffelt RF-10 unit was used since a rotating field with pulsed DC current is reasonably effective under these conditions. The-unit employed a 4.0 kilowatt, 220 volt generator as a power source. A smaller unit of 1.8 kilowatts was also used on a raft in canyon areas. Conductivities fluctuated during the year, requiring frequent adjustment of the electrical equipment. Electroshocking gear was especially useful in collecting Colorado squawfish, a species which appeared to be more vulnerable to electroshock than others. Another unit (Coffelt VVP-15) was employed as a replacement of the RF-LO unit in 1981 and proved more effective. Trammel nets were set in slow-flowing runs and eddies. These nets were tended regularly, from one to three hour intervals depending upon temperature and conditions. Gill nets were occasionally used as supplemental gear but were generally discontinued. The trammel nets were 1 in and 1.5 in bar mesh, I50 ft long x 6 ft deep with a wall of 10 in to 12 in mesh, respectively.