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<br /> <br />I <br /> <br />17 <br /> <br />A radio tagging program is to be initiated to better follow <br />spawning behavior of squawfish and to define specific spawning areas <br />so as to determine the constituents of spawning habitats. <br /> <br />An assessment of disease organisms affecting the endemic as well <br />as the introduced species will be carried out during 1980. These <br />investigations will be conducted on a cursory plane by field crews and <br />intensively by a group of disease specialists who will sample all <br />major components of the populations in both rivers three times a year <br />for all major pathogens and parasites. <br /> <br />Humpback chub YOY studies and movement patterns will be addressed <br />by our team in cooperation with the Colorado Division of Wildlife. <br /> <br />Equipment <br /> <br />The field teams were faced with the very challenging task of <br />effectively sampling a very extensive river system under some very <br />difficult conditions. To do this the most advanced technological <br />equipment was utilized to collect fish and to measure the associated <br />chemical and physical parameters (Appendix A-2). <br /> <br />The effectiveness of electroshocking equipment is diminished <br />substantially by the high conductivities, great depths and high <br />turbidites. However, a unit was developed using a rotating field with <br />pulsed DC current which was reasonably effective under most conditions. <br />The unit used a 4.0 kilowatt generator as a power source. A smaller <br />unit of 1.8 Kilowatts was developed for use on a raft, but it had very <br />limited effectiveness. Fish collection with the larger unit was <br />generally most.effective at 200-250 volts and 8 to 12 amps. Condunctivities <br />fluctuated extensively requiring continual adjustment of the electrical <br />equipment and electrodes. This gear was especially useful in collecting <br />squawfish which appeared to be more vulnerable to electroshock than <br />most of the other species. <br /> <br />Trammel nets were set in the slow-flowing pools and eddies. They <br />of course often collected much debris but were effective on squawfish, <br />chubs, suckers, catfish and carp. They rarely caught intermediate and <br />small fishes. Because fish generally succumb in this gear after a <br />short while, They were tended regularly every two to three hours. <br />Gill nets were only occasionally used because they have been credited <br />with being more lethal to fishes. This, however, was not borne out in <br />our experiences and we feel that in all likelihood they are less <br />destructive to the rare fishes than trammel nets. <br /> <br />The trammel nets we utilized were 150 ft long x 6 ft deep and of <br />1 in and 1.5 in bar mesh of #139 twine with a wall of 10 to 12 in bar <br />mesh. <br /> <br />Funnel-type wire mesh traps of 1 in chicken wire approximately <br />1.5 ft in diameter by 2 1/2 ft long were very effective when set among <br />large boulders or accumulations of debris in catching catfish and the <br /> <br /> <br />