1 1 . ) “ Observations on the effectiveness and maintenance of the Highline Lake fish barrier net . ”

A 363 foot wide x 19 foot deep x 0.25 inch aperture spillway barrier net fabricated of Dynema was installed in Highline Lake in August 1999 to control escapement of juvenile and adult nonnative fish. The net’s placement met the screening requirement in the Procedures for Stocking Nonnative Fish Species in the Upper Colorado River Basin and allowed the stocking of bluegill and largemouth bass into Highline Lake in 1999 and 2000. Fish sampling and marking was performed in Highline Lake to evaluate fish escapement from the reservoir and downstream movement of nonnative fish toward the Colorado River. Fish were captured in June of both 1999 (1,091 fish=100% nonnative) and 2000 (1,420=99% nonnative), measured for total length, weighed and given a right pelvic fin clip (except trout) to denote their origin in the reservoir. Largemouth bass stocked into the reservoir in September of 1999 (7000 @ 4.2 in.) and 2000 (7000 @ 4.0 in.) were also marked with right pelvic fin clips. Monitoring of the net’s performance included observations on 1) maintaining a seal between the net’s bottom skirt and the lake bottom, 2) sand and gravel being wave-washed onto the net nearshore, and 3) the net’s main float-line submerging during a period of high flow through the reservoir. Aspects of the net’s maintenance discussed include 1) estimated vs. actual expenditures for inspections and cleaning in 2000, 2) the decision to leave the net in place over-winter vs. removing it, and 3) correcting the tendency for the net’s top-skirt to sag and adjoin the net’s main float line. Electrofishing was conducted at three sites, in Mack Wash below Highline Lake’s dam, in Mack Wash near Root’s Reservoir, and near Salt Creek’s confluence with the Colorado River, in 1999 (JulyNovember) and 2000 (MayNovember) to evaluate the net’s effectiveness in controlling fish escapement from the reservoir. Following the net’s installation, few marked fish were captured downstream of the reservoir in 1999 (4 of 714 = 0.5%) or 2000 (8 of 1565 = 0.5%). The number of largemouth bass captured in the reservoir nearly doubled from 1999 to 2000 (69 to 120) while the number of bass captured below the dam in 2000 was about half those captured in 1999 (230 to 127). The low number of marked fish captured below the dam, particularly stocked largemouth bass (3 @120-130 mm in 1999 and 7 @ 80-130 mm in 2000), suggests the net is highly effective in controlling escapement of fishes from the reservoir. Limnological sampling identified an opportunity to consider rescheduling annual maintenance releases from the reservoir’s unscreened bottom outlet from early spring to mid-summer when low dissolved oxygen levels would preclude or minimize fish escapement. 2.) "Non-native fish control in backwater habitats in the Colorado River, Colorado" Melissa Trammel, SWCA, Flagstaff AZ ABSTRACT—Valdez, R., L. Jonas, M. Trammell. 2000. Non-Native Fish Control in Backwater Habitats in the Colorado River. Recovery Implementation Project No. 87b, 1 SWCA, Inc., 172 West 1275 South, Logan, UT 84321, 2 SWCA, Inc., 114 N. San Francisco Street, Flagstaff, AZ 86001Valdez, R., L. Jonas, M. Trammell. 2000. Non-Native Fish Control in Backwater Habitats in the Colorado River. Recovery Implementation Project No. 87b, 1 SWCA, Inc., 172 West 1275 South, Logan, UT 84321, 2 SWCA, Inc., 114 N. San Francisco Street, Flagstaff, AZ 86001 Predation and competition between small, non-native cyprinid species and young endangered fishes has been demonstrated in laboratory experiments (Ruppert et al. 1995; Muth and Beyers, unpublished data), and is perceived to be influential in limiting survival and recruitment of razorback sucker (Xyrauchen texanus) and Colorado pikeminnow (Ptychocheilus lucius) in the wild. Lentsch et al. (1996) recommended seining of select habitats as a viable mechanical control option for introduced cyprinids such as red shiner, fathead minnow, and sand shiner. The objectives of this study are to: 1) Significantly reduce the abundance of small non-native cyprinid and centrarchid fish species present in