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to !De critir'j as to t. rthnr ±h® aroa ,mill{ hP tt+iji,car{ , pn,iomir (`nlnv?rlrZ <br />..., _.. _ . _ .. .. ... 4... ..J ._ .;.., <br />squawfish and Razorback suckers. <br />Migration barriers are frequently mentioned as a major reason for the <br />drastic decline in numbers of Colorado squawfish and Razorback sucker. <br />Figures 4 and 5 show locations of irrigation diversions along with locations <br />of documented catches of both species. <br />Tagging studies in the study area seem to indicate that if all habitat <br />requirements are present in a localized area, the fish do not move very far. <br />Returns for the 70 Razorback suckers that were tagged with numbered spaghetti <br />at Walker Wildlife Area in 1974-75-76 showed only one of nineteen recaptures <br />had moved out ttt of the area. This one -a t.as rorantutod t nm tho f i i ftnn har ,_ <br />r_ fr s vest t.: tt. •s s t s •. e.ree utie? <br />water area during the 1975 sampling season. Tagged squawfish displayed a <br />similar lack of movement, but because it was impossible to tag sufficient <br />numbers, results are not conclusive (1975, Karl Sethaler, personal communi- <br />cation ). <br />Water Quality and Quantity <br />Data on water quality and ranges in river flow are difficult to evaluate. <br />Data from key locations for calendar year 1975 is-presented in Table 5. The <br />range in values presented is a clue to the wide variation in habitat the <br />fish tolerate. <br />The importance of irrigation return drains within the Grand Valley is <br />shown in Table 6. The high values for TDS in the water add significantly to <br />the Colorado River salinity. It is also interesting to note that fish survive <br />and live in these areas as shown in the data presented in Table 7. Although <br />none of the four key species of endemic fish were in these collections, one <br />can not positively state that they are Ppresent. However, the author believes <br />(19)