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I I I I I I I I I I I I I I I I I I I EXECUTIVE SUMMARY This report describes the findings of a fishery study conducted to monitor the Lake Powell inflow of the Colorado River before and after spring runoff to determine if significant numbers of age-O Colorado squawfish (Ptvchocheilus lucius) and larval razorback suckers (Xvrauchen texanus) are being transported into the area. One hundred and one Colorado squawfish, including 9 larvae, 51 age-O, 36 juvenile and 5 adults were captured in the Lake Powell inflow in 1993. Densities of age-O Colorado squawfish found in April 1993 in the Lake Powell inflow were similar to densities recorded in the Green and Colorado rivers above their confluence during spring 1993 ISMP sampling. Geometric mean CPE for pre-runoff sampling was 1.05 age-0/100m2. This compares with densities of 0.92 age-O /100m2 for 3S miles of the Colorado River above the confluence and densities of 1.03 age-0/100m2 for the lower 120 miles of the Green River. Use of larval light traps increased sampling efficiency in the lentic habitat of the inflow region. This sampling device proved very successful in capturing young fish in areas previously unsampled with conventional sampling gear (i.e. seines and gill nets). Light traps were used in the Lake Powell inflow to collect fifteen suckers preliminarily identffied as razorback suckers (identification pending genetic analysis) and nine larval Colorado squawfish. Use of larval light traps in future sampling will greatly aide in estimating numbers of larval Colorado squawfish and larval razorback suckers transported into Lake Powell. Other native fish species found in the Lake Powell inflow were bluehead sucker, flannelmouth sucker, speckled dace and Gila m. The 33 Gila captured during post-runoff sampling were all classified as age-O fish and likely originated from Cataract Canyon. The capture of Gila in the Lake Powell inflow is significant because it indicates that the region may also influence age-O humpback, roundtail and possibly bonytail chub moving downstream from Cataract Canyon. ill