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reasonable means to supplement distributional data and increase sample sizes, effective chub monitoring requires trammel netting. Drift net sampling.-Drift net sampling was conducted in the Green River just upstream of the Yampa River in each year of 2002 to 2004 period, as well as in 1994 and 1995. No early life stages of Colorado pikeminnow were captured in any year that drift net sampling was conducted. We detected two putative razorback sucker x white sucker hybrids, one in each of 2003 and 2004; these individuals were 33 and 30 mm TL, respectively. Based on spawning ecology of Colorado pikeminnow and water temperatures that were present in the Green River in Lodore Canyon, pikeminnow should have been able to spawn there in all years of this study (Nesler et al. 1988, Bestgen et al. 1998). Drift net sampling conducted in the adjacent lower Yampa River in each of those years detected reproduction by Colorado pikeminnow, based on capture of larvae. Some unknown habitat differences or low numbers of ripe adults may explain the apparent absence of spawning by Colorado pikeminnow in the Green River in Lodore Canyon. Putative razorback sucker x white sucker hybrids that we captured in drift nets set in lower Lodore Canyon in 2003 and 2004 were identified with traditional morphological analysis (Snyder and Muth 2004). We plan to verify the taxonomic identity of those putative hybrids more fully with genetic analysis. If that identification is verified, it would represent the first documented hybridization between those sucker species. Regardless, expanding populations of white sucker may pose an additional threat to razorback sucker recovery efforts. White suckers in the San Juan River system have been established in the Animas River for many years (Platania et al. 1987; 1988) but remain rare in the downstream main stem of the San Juan River (pers. comm., D. Propst, New Mexico Dept of Game and Fish). Few fish species and individuals were captured in drift net samples in 1994 to 1995, but species diversity and number of fish captured increased substantially in the period 2002 to 2004 (Table 9, Fig. 43). Sampling effort also increased in the 2002 to 2004 period. In 1994 to 1995, six species were captured and > 90% of those individuals were native. Up to 16 species were 47