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6 I I I I I I I I I I I I I I I I I I I The traps were manufactured by Ed Tyberghein (Southern Concepts) and are similar to the Quatrefoil trap described by Floyd et a!. (1984) and modified by Mueller et al. (1993). Tyberghein's light trap is 305 rom tall, 250 mm in diameter with a slit width of =3 mm. The design incorporates a styrofoam top that allows the trap float and a 2.25 V bulb as a light source. Power is provided by two D-ccll batteries and output can be maintained for 30-40 hours. Light traps were set at dusk in slackwater habitats and allowed to fish all night. Traps were pulled before dawn since daylight allowed the fish to move back out of the traps Capture data for both the NPS samples and post-runoff sampling are included in this report. All fish captured in light traps were identified by the Larval Fish Laboratory at Colorado State University. Due to the large numbers of nonnative larvae (i.e. red shiner, sand shiner and fathead minnow) in the samples, only native species were counted. Catch rates for larval light traps are presented as number of fish per 100 hours of sampling (fish/1oo hr). Total catch rates are computed by dividing the total number of fish by the total time sampled. 3.3 STOMACH CONTENT ANALYSIS Stomach analysis were performed on all predatory species caught electro fishing and seining. Only predators over 125 mm TL were examined since Colorado squawfish were approximately 10-11 months old and 45-75 mm TL. Stomach contents were preliminarily identified in the field when possible and preserved in 70% ethanol. Final identification of stomach contents was performed by BIO/WEST. 3.4 DATA COLLECTION AND STORAGE All data collected in the field were recorded on standard forms using codes consistent with the Upper Colorado River Basin Database Codes (UFWS 1987). The data forms used and a list of field codes are presented in Appendix A The data were stored in the database management system dBase IV 1.1. 4.0 RESULTS 4.1 SUMMARY OF FISH COLLECTIONS A total of 18 species of fish representing 8 families, were captured in the Lake Powell inflow in 1993 (Table 2.) This list is similar, though not as extensive as that reported for collections in the region in 1985-1988 (Valdez 1990). As percentage of total catch, the most common species captured in the inflow region were red shiner (41.3), sand shiner (35.5), common carp (6.6) and fathead minnow (6.3). These 4 non-native species comprised 89.7% of the catch. Native fish species captured in the Lake Powell inflow included; bluehead sucker, flannelmouth sucker, razorback sucker, Colorado squawfish, Gila m. and speckled dace. All these species combined comprised only 4.2% of the total catch.