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1 1 1 in 1997 and 1998. Most spawning occurred during peak flow levels and when water temperatures were rising. Flow levels during spawning were variable within and among years and water temperatures were generally in the 10 to 17°C range. Environmental conditions during spawning were similar to those during other sampling years since 1993 (Table 8). In general, razorback suckers spawned in the middle Green River from mid-April to mid-May when water temperatures were 10 to 16°C and when accumulated degree days ranged from about 400 to 900. Spawning generally began 5 to 36 days prior to day of highest spring runoff flow and nearly always before water temperatures reached 14°C. In 1997 and 1998, most larvae were captured when spring runoff flows were declining. Only in 1999 did timing of high flows correspond with occurrence of most razorback sucker larvae in samples, a year in which few larvae were collected. Larvae, lower Green River.-In the lower Green River from 1996 to 1999, a total of 41,829 fish in 13 taxa were captured in light-trap samples (Table 9). Of those, 6,824 (16.3 %) were native catostomids (included all unidentified sucker larvae), and 304 (4.4 %) were razorback sucker larvae. The number of native catostomid larvae captured varied from 146 in 1997 to 2,666 in 1998. Sampling effort and number of catostomids captured was positively correlated (r = 0.93) with sampling effort for 1996 to 1999. In 1993 to 1999, a total of 72,864 fish were captured using all sampling gear types. Of those, 8,343 (11.5 %) were sucker larvae, and 530 (0.7 %) were razorback suckers. Light-trap sampling data showed high variation in eatostomid abundance as the number of catostomid larvae captured varied from 122 in 1993 to 2,666 in 1998. Capture rates of catostomid larvae were positively correlated with sampling effort (r = 0.80) from 1994 to 1999. The CPUE for all native suckers varied considerably by year and was mostly a function of changes in abundance of 18