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minnows (Pimephales promelas) and red shiners (Riggs et al. 1987). Granath and Esch (1983b) found that mortality as a result of Asian tapeworm infestation was a function of parasite density and host size. As nonsegmented worms were exposed to higher water temperatures and grew, the smaller and more heavily infected hosts died. If temperatures in the Colorado River increase and tapeworms mature, these same effects may be seen in humpback chub that have high parasite loads. Praziquantel bath treatments will be essential for monitoring changes of tapeworm infestation in humpback chub that are likely to occur if management actions are implemented to warm the manistem Colorado River water. Asian tapeworm probably only recently invaded the Little Colorado River and were not present for very long in the system prior to its fIrst detection in 1990. Many humpback chub were dissected for diet analysis and parasite investigations prior to 1990 but Asian tapeworm was not found (Table 5). In July 2005 Asian tapeworm was discovered in young-of-the-year carp above Grand Falls on the upper Little Colorado River indicating that Asian tapeworm may have come into the Little Colorado River in Grand Canyon from upstream reservoirs (Stone et al. 2005, In Review). The most recent investigation of Asian fIsh tapeworm in the Little Colorado River (Choudhury et al. 2004) only looked at infestation in humpback chub <150 mm TL because examination required fIsh to be dissected. That study found an average of 18 tapeworms per fIsh. Our results showed little if any tapeworm infestation in fIsh <150 mm TL. The reason there is a difference in these results may be related to Little Colorado River hydrology, The winter and spring flooding in the Little Colorado River, in 2005, were probably not conducive to copepod survival, whereas in 2001, low flow and blue water conditions would have been very conducive to high numbers of copepods.