9668 - Laserfiche WebLink

Home Browse Search

Depth Selection In Substrate and Flow Experiments During the day observations, bonytail were at deep depths 100% of the time. There were not enough night observations at middle and shallow depths to run an R x C test. Bonytail were selecting for deep depths invariantly. Substrate Experiments With Red Shiners Since bonytail showed a strong preference for cobble substrate in previous experiments, cobble was used in each replicate. Bonytail were not displaced by the presence of red shiners. Substrate selection was independent of the time of observation as determined by an R x C test (x2=0, df=2, p=5.991). As without shiners, bonytail were found exclusively in the cobble substrate in both day and night (Fig. 1.2). Depth Selection In Substrate Experiments With Red Shiners Depth selection was independent of time of observation (day versus night) as determined by an R x C test (?& 0, df=2, p= 5.991). Bonytail showed a significant preference for deep depths during both the day and the night, and were found at deep depths 100% of the time (Fig. 1.4). Flow Experiments With Red Shiners Two-way ANOVA results, with the presence/absence of red shiners and three different velocities (see above) as the two treatment variables, revealed a significant interaction for velocity selection as a consequence of red shiner presence/absence (F=108.06, p=0.0001). At low and high velocities, bonytail selected higher flows in the presence of red shiners relative to controls (Fig. 1.5). At intermediate velocities, bonytail selected lower velocities in the presence of shiners. To further interpret these interactions, we used the coefficient of variation of selected velocities as the dependent variable in a similar two-way ANOVA. The results of that test revealed the same result with a significant interaction between shiner presence/absence and available velocity (F= 3.55, p=0.0346). When red shiners were absent, bonytail showed decreased variation for velocity selection as a function of increasing available velocities. When red shiners 21