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DISCUSSION Comparison of drift results from Loma, Westwater and Moab Drift densities at Westwater and Moab were also compared with the concurrent larval drift sampling conducted on the Colorado River within Colorado (Anderson 1999). For the three drift sampling stations in Colorado above Westwater, Colorado pikeminnow density increased in a downstream direction. Neaz the confluence of the Gunnison River, catch rates were zero to near zero between 1994 and 1996. At the Middle Station just 5.1 km downstream catch rates increased, ranging from 1.0 to 10.2 CPM/1000 m3 between 1994 and 1996. Catch rates increased at Loma by 67% to 400% over the Middle Station during the same three-yeaz period. The increase in Colorado pikeminnow larval numbers in a downstream direction suggests that there was at least one Colorado pikeminnow spawning site located between the Middle and Loma Stations. Seasonal drift densities for Colorado pikeminnow larvae at Loma were not correlated with Westwater drift densities 48.3 km downstream either in catch per 1000 m3 (r2 = 0.022; Table 8), or in total transport abundance (rz = -0.43). The lack of a correlation indicates differential trends between years at these two sites. At Westwater the higher flow yeazs had higher Colorado pikeminnow densities with the highest in 1993, and the third highest in 1995, while in Loma this was reversed with the highest in 1995 and the 3'~ highest in 1993. The low flow years (1992 and 1994) ranked 4~' and 5~', respectively in Westwater but the ranking was 2°a and 4~' respectively at Loma. The largest discrepancy in ranking was in the intermediate flow year (1996) which ranked 2"~ at Westwater but was 5`~ at Loma (Table 8). The lack of a correlation between Loma and Westwater results does not support assumptions that upstream (Loma) drift densities influence downstream abundance or that Loma and Westwater are sampling the same larval population, offset temporally. With current velocities of only 0.9 m/sec, passively drifting larvae could move between Loma and Westwater in less than 24 hours. However, peaks in larval collections at the sites were not consistently offset temporally. Also, the onset of spawning occurred eazlier at Westwater than at Loma in 4 out of 5 years, and earliest at Moab in 3 of 5 years. Either different larval populations were sampled, or the sampling efforts at one or more stations were not representative of the actual larval population size. The differences could be partly attributed to an artifact of data manipulation, because seasonal densities are difficult to standardize due to the large number of zero-fish days. Catch rates and total transport abundance were calculated for the 26 highest fish days at Loma, which included all the days Colorado pikeminnow were collected. However, at Westwater and Moab, catch rates were calculated from the first to the last day pikeminnow were collected, which was frequently longer than 26 days. Use of a standazd 26 days would either raise or lower yeazly catch rates by the subtraction or addition of zero-fish days, or pikeminnow collection days. However, this manipulation would not change the basic relationship of catch rates, which declined between Loma and Westwater, and increased between Westwater and Moab. Catch rates in both fish/1000 m3, and total transport abundance were lower at Westwater than at Loma in all five years (Table 8). This may indicate that Colorado pikeminnow larval mortality exceeded recruitment between Loma and Westwater, although the Westwater station 15