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Electrofishinn near was emnloyPH thrniinhmit the entire study area. <br />Electrofishing gear enables one to sample a number of areas of a river where <br />other types of gear, such as trammel nets and seines, are ineffective or <br />impossible to use. The entire stretch of t,ie uunni son and 10 mi 3 es .of t;Ie <br />Colorado River were electrofished at least once. However, electrofishing <br />gear is considered to be one of the least effective methods in this area of <br />the Colorado River system to collect the large river endangered and threatened <br />fish species (Kidd, 1974). <br />A total of 30 sampling trips utilizing 80 man days were involved in <br />the collecting efforts in Colorado. Ten sampling trips and 25 man days <br />were spent on Utaih „ r-tiOnS <br />Several basic problems were inherent to the study. Fish sampling tech- <br />niques for large rivers are at best inadequate. Couples with this is the <br />care that must be taken to avoid mortalities when attempting to collect <br />threatened and endangered species. Methods of collecting such as toxicants, <br />explosives and other methods which cause excessive fish mortalities could <br />not be employed because of the possibility of eliminating the populations <br />being studied. The second major problem was the length of the study. Since <br />the period of study covered 10 months out of a populations life history, only <br />relative general conclusions can be made regarding prefered habitats. Because <br />of this, many of'the statements and conclusions drawn from this study are <br />those of N.F.R.I. <br />Macro invertebrates were collected and evaluated on the basis of approxi- <br />mately 9 square foot of bottom samples. A surber square foot bottom sample <br />was used to collect samples. Riffle areas were selected and varied in depth <br />from 3-10 inches. Riffles were selected because of sampling ease and the <br />assumption most fish utilize these areas for feeding. <br />(10)