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and analysis to that portion of the fish community consisting of species with individuals > 100 mm TL. Relative abundance of small, backwater-dwelling minnows (e.g., Pimephales promelas, Cyprinella lutrensis, Notropis stramineus), the primary forage for sub- and young- adult Colorado pikeminnow (< 550 mm TL), is monitored annually as part of other studies (e.g. McAda et al. 1994) and therefore was not investigated here. We sampled the fish community each spring and fall of 1994 and 1995. Sampling during the first season (spring 1994) consisted of a pilot effort and therefore yielded only a partial data set (strata 4, 6, 9 and 11 were sampled). In both years sampling occurred during base-flow periods: in spring, between March 7 and April 28; in fall, between September 7 and October 24 (Appendix Table 2). Within each study reach, both shorelines were electrofished in a downstream direction. Within seasons, the same boat was used for both shorelines, sometimes on the same day; sometimes on different dates. In most cases a 5-m, hard-bottomed, electrofishing boat was used. In reaches containing rapids, a 5-m, rubber raft outfitted for electrofishing was sometimes used. Each type of boat was equipped with a Coffelt WP-15 (Coffelt Manufacturing, Flagstaff, Arizona) that produced pulsed DC. Total elapsed time electricity was applied along each shoreline sample was recorded in seconds by an automatic counter on the WP, Whether rowed or motored, every effort was made to maintain a constant boat speed. Because fish were abundant in strata 7-12, two people with long-handled dip nets were stationed on the bow of the boat to net stunned fish; however, in strata 1-6, where fish were few, only one person netted fish. Each shoreline within each subreach was treated as a separate sample, resulting in six samples per stratum. Netted fish were transferred to one of two live wells on the boat and held until a shoreline sample was completed: fishes from run habitats went in one live well and fishes from riffles went in the other. Elapsed shocking time through each habitat type was counted on the WP meter and recorded on data sheets at the time of sampling, i.e., each time a run ended and a riffle began (and vice versa), the number of seconds was recorded and the counter was reset to zero. At the bottom of the reach, fishes were identified, measured for total length (to the nearest millimeter), weighed with an electronic balance (to the nearest gram), and released. Catch-per-unit-effort (number of fish caught per minute of electrofishing) was calculated by dividing the total number of fish (either in aggregate or by species) by total shocking time for each electrofishing sample; values for all samples within a stratum were averaged to provide a mean catch rate for that stratum. Comparisons of catch rates among strata were made both for all fish and for only those deemed vulnerable to Colorado pikeminnow predation. We assumed that because of their large size, many adult fish were not vulnerable to predation by Colorado pikeminnow. We therefore partitioned fish by size, omitted the larger size classes (> 300 mm TL, see below), and then compared catch rates among strata. The maximum size of prey a given size of Colorado pikeminnow can consume is unknown. For fusiform-shaped prey, maximum prey size is probably not limited by predator gape width but rather by prey body length or mass (Osmundson 1987). We assumed Colorado pikeminnow could consume prey up to half their own length (e.g., Juanes 1994, Osmundson et al. 1998), and therefore fish