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Length weight relationships of both the humpback and roundtail chubs developed in the current study were compared with pre-project data (Appendix Figure ). The exponents for humpback chub were in excess of 3 during the years prior to the current study indicating isometric growth, similar to the relationship reported for the Grand Canyon population (Valdez and Ryel 1995). During the current study the slope of the relationship decreased (exponent = 2.75) indicating a shift towards slightly smaller individuals and perhaps poorer condition. Mean length of humpbacks collected between 1987 and 1989 was 283.9 mm, with the largest individuals collected in 1987 (mean TL = 319.7mm), which greatly influenced the length -weight relationship. The current study mean total length was 277.7 mm. A similar trend was found with the roundtail length- weight relationship. Svmpatric Species Channel catfish were the most abundant sympatric species in main channel habitats (trammel net catch) ,however at 14.3% of the total catch were much less abundant than native chubs (refer to figure 13). Native suckers (flannelmouth = 3.2 % and bluehead = 7.2%) were the next most abundant species followed by common carp which only comprised 2.3% of the trammel net catch. Despite the abundance of native chubs, only ten Colorado squawfish were collected in the nets throughout the study accounting for 0.4% of the total. Incidental collections of white sucker, brown trout and several centrarchids, individually comprising less than 1 % of the catch, completed the catch list. In the shoreline sampling (electrofishing and hoop netting) the catch was more diverse (refer to Figs. 12). Again native chubs in the aggregate accounted for the majority of the catch, however common carp were the next most abundant species accourning for 8.5% of the electrofishing catch. Native suckers were better represented than in the trammel nets and more abundant than channel catfish. Largemouth bass (n=9), which were not collected in trammel nets, were picked up electrofishing. Various age classes of channel catfish were encountered in Westwater Canyon and large individuals (TLa400mm) were collected regularly. Their numbers fluctuated throughout the study. They were most abundant at the upper site indicating they may be entering Westwater Canyon from upstream. However, as discussed above, channel catfish never comprised a very DRAFT 37