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".. . 1 bass (<8 cm), yellow bullhead (<14 cm), channel catfish (<13 cm) and bonytail (<8 cm) were all found to be aggressive predators of 10-50 mm razorback sucker. INTRODUCTION This past year (2003) represented the second ofa four-year field effort designed to describe the early life ecology ofbonytail and razorback sucker in CHLP. Last year we conducted extensive surveys aimed at measuring standing crop of the native fish community. Both species had successfully produced young and the community was estimated to include approximately 1,100 razorbacks and 6,000 bonytail (>15 cm)(www.fort.usgs.gov/oroducts/oubs/11000/11000-A.odf). The pond's standing crop was 4,350 fish/ha with a biomass of 635 kglha. In 2002, bonytail continued to produce young but we did not detect any measurable recruitment during the past two years for razorback sucker. The following description of work is grouped into four categories. Telemetry studies were conducted on adult bonytail from mid-March through early May. The goal was to examine movements, behavior, and locations frequented by adult bonytail during their suspected spawning period. The second major activity was to use underwater videography to verify suspected spawning sites, monitor spawning behavior, determine timing of peak: spawning activity and document possible predators. The third category included physical measurements, trammel netting, light trapping, water quality monitoring, map surveys and acoustical tests. Mapping survey results will be incorporated into the telemetry results to refine movement data. Data collected for these efforts is currently being analyzed and will be presented in next year's report. We also conducted a series of predator/prey tank tests to identify potential predators observed in CHLP and to examine suspected nonnative predators found elsewhere in the basin. This work is being conducted at, and with the cooperation ofthe staff at USFWS Willow Beach National Fish Hatchery and at Achii Hanyo Fish Facility. BONYTAIL TELEMETRY WORK Methods On 18 March 2003, 11 adult bonytail were collected from four sets of trammel nets distributed throughout the pond. Their sizes ranged from 358 t6 514 mm. Ten fish (404 to 514 mm [x=453 mm]) were fitted with a sonic micro transmitter (8x35 mm). Due to limited battery life (60 d), transmitters were externally attached to the fish to avoid convalescence that is necessary with surgical implantation (photo 1). 3