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<br />4 <br /> <br />Physical - Chemical Parameters <br /> <br />Physical and chemical data were collected during each sample period <br />between 1100 and 1400 hours. River depths were recorded with a Lowrance <br />Model LRG 1510-A sonar depth finder (graph type)," except in shallow <br />conditions (<1 ft) where a Philadelphia rod was used. Depth transects <br />were made perpendicular to the thalweg of the river. River width was <br />measured at the site of each depth profile using a range finder or <br />estimated by eye. Water temperature, air temperature, specific <br />conductance and salinity were measured with a Yellow Springs S-C-T Meter, <br />Model 33. Dissolved oxygen content was determined with a Hach Model <br />OX-lO analysis kit. <br /> <br />Watercraft <br /> <br />Several types of watercraft were used depending on river flow. <br />Aluminum flatbottom boats (14 and 16 ft Lowe@) were used most of the year <br />on the Gunnison River. Hypalon rafts (16 ft Campways@ Miwok) were used <br />on the Dolores River because of dangerous rapids and low flows. Rafts <br />were also used during low water on the Gunnison River. Low water levels <br />in the Dolores River in August 1981 necessitated the use of a canoe for <br />carrying sampling equipment. <br /> <br />Sample Gear <br /> <br />Active and pass~ve gears were used to capture fishes. <br />Electrofishing, trammel nets, gill nets, fyke nets and beach seines were <br />the major gears used. Several gear types were used in orde~ to <br />adequately sample different habitats (Table 1). These gear types were <br />prone to differing rates of efficiency in capturing fishes. <br /> <br />Table 1. Principal Gears Used by CRFP to Sample Fish Habitat ~n the <br />Upper Colorado River. <br /> <br />Gear <br /> <br />Habitats <br /> <br />Electrofishing <br /> <br />run, rifle, shoreline, side channel, large <br />backwater, mid-channel <br /> <br />Trammel and gill nets <br /> <br />pool, eddy, large backwater, slow run, <br />mid-channel <br /> <br />Seines <br /> <br />small backwater, shoreline, run, riffle, pool <br /> <br />Electrofishing <br /> <br />Boom-type electro fishing units were built on 16 ft flatbottoro boats <br />or 16 ft hypalon rafts. A 5-kw generator was mounted on a small <br />aluminum frame in the back compartment of the raft or bolted on wood <br />planks in the middle compartment of the boats. Electricity was regulated <br />with a Coffelt@ RF-IO electrofishing unit. Pulsed DC current was <br />