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4 I I I I I I I I I I I I I I I I I I I 3.0 METHODOLOGY 3.1 BASIC STUDY DESIGN The Lake Powell inflow of the Colorado River was sampled twice in 1993, once in April before spring runoff and again in August when Colorado River flows had returned to base levels. The objectives of pre-runoff sampling were to measure densities of age-O Colorado squawfish prior to spring runoff and to assess levels of predation on age-O squawfish. The purpose of the post-runoff sampling trip was to measure densities of age-O squawfish after runoff and to again assess predation on age-O squawfish. Each sampling trip was 5 days long. A crew of four biologists (2 NPS and 2 BIO/WEST) participated in each trip. Pre-runoff sampling was conducted April 19 - 23, post-runoff sampling August 2 - 6, 1993. Two additional sampling trips will be conducted in 1994 at approximately the same time 3.2 SAMPLING GEAR Electrofishing, seining, nets and passive light traps were used to capture fish in the Lake Powell inflow. A brief description of each and its associated data gear code are presented in Table 1. Table 1. Description of fish sampling gear used in the Lake Powell inflow Study, 1993. GEAR CODE DESCRIPTION Electrofishing EL 220-volt DC with Coffelt VVP-15 on 16' aluminum Jon boat Trammel Net TK 75' x 6' net with 1" mesh Gill Net GP 100' x 6' net with 1" mesh Seine SB SE 15' x 4' with 1/8" delta mesh 10' x 4' with 1/16" delta a mesh Light Trap LT Floating clear plastic trap with integral light source (quatrefoil design) 3.2.1 Electrofishiol! Electrofishing was used to capture adult and juvenile fish along shorelines and return channels. All fish were captured using a Coffelt VVP-15 pulsed DC electrofishing unit, with a duty cycle of 20% and a pulse rate of 40 Hz. Normal operating level was 190-220 volts and 8-10 amps. This system was operated from a 16 ft aluminum Jon boat and powered by a 5500 watt Yamaha generator. Anodes of three-pronged 1/4-inch stainless steel braided cable were used. Catch rates for electro fishing were calculated by pooling the data. This method is simply the total number of fish divided by total time sampled. CPE's are expressed as number of fish per 10 hours of electrofishing.