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Temporal variation All fish.--Riverwide, mean total catch rate in fall 1994 was significantly higher (T-K, P < 0.05) than in spring or fall 1995. Within some strata, mean total catch rates (all fish combined) were fairly similar among sampling periods; in others, they were not. In downstream strata 1-6, where catch rates were generally low, the mean total catch rate appeared to decline between fall 1994 and fall 1995 in strata 2 and 3 (Figure 5), but not in other strata (no within-stratum differences were significant; T-K, P < 0.05). In upstream strata, mean catch rates were generally more variable through time. In Stratum 9, mean total catch rate was significantly lower (T-K, P < 0.05) in spring 1995 than in spring and fall 1994 (Figure 6). Also, in Stratum 12, mean total catch rate in spring 1995 was significantly lower than in fall 1994 and fall 1995. The species with greatest catch rate variation over time appeared to be bluehead sucker (variation by species was not statistically tested). Prey-size fish.--In comparison to total fish, there was generally more temporal variation in numbers of forage-size fish. Riverwide, the three primary sampling periods were significantly different (T-K, P < 0.05) from one another in mean total catch rates of fish 100-300 mm TL. For the four strata sampled during all four study periods (strata 4, 6, 9 and 11), catch rates in fall 1994 were significantly higher than in the other three periods. In downstream strata, variability in mean catch rate among sampling periods was largely determined by fluctuations in numbers of young blueheads (Figure 7), the species with the most forage-size individuals. However, mean total catch rates were not significantly different among periods within any of the downstream strata. In upstream strata, where several species had forage-size individuals, variability in catch rate among sampling periods resulted from changes in abundance of each species, and each stratum displayed a somewhat different sequence of changes (Figure 8). However, only in strata 9, 10, and 11 were there significant differences among sampling periods. In Stratum 9, catch rate in fall of each year was significantly higher than in the preceding spring. Increases in both fall periods were due largely to increases in young flannelmouth and bluehead suckers. In Stratum 10, the mean total catch rate in spring 1995 was significantly lower than in the previous fall. This decline involved all species. In Stratum 11, the catch rate in fall 1994 was significantly higher than in the other three periods. There, catch rates of forage-size bluehead suckers were very low through all periods and catch rates of flannelmouth and white suckers and roundtail chubs varied very little. Temporal changes in total catch rate in Stratum I 1 was primarily influenced by changes in the number of salmonids (mostly mountain whitefish). In fact, with the exception of fall 1994 when there was a pulse of young mountain whitefish, catch rates of forage-size fish in Stratum 11 were comparatively low. Catch rates in the Gunnison River study stratum were high during both fall sampling periods, and significantly lower during the intervening spring (1995). There, catch rates of white suckers, roundtail chub and trout (no mountain whitefish were captured in the Gunnison River) were essentially stable between each fall, while numbers of young flannelmouth and bluehead suckers were more varied. 13