7769 - Laserfiche WebLink

Home Browse Search

instances. Correlations between gmean CPE for Colorado squawfish and backwater maximum depth were generally very weak and not significant. Only one significant relationship was found-a weak, negative relationship (r=-.34) in Reach 4 during 1988 (Table B-10). Temperature preferences of YOY Colorado squawfish were evaluated based on the temperature of the backwater when sampled and the difference in temperature between the backwater and the main channel. Descriptive histograms were developed based on 1 °C intervals. ANOVA was based on four categories (9 to 15°C, 16 to 19°C, 20 to 23°C, and 24 to 32°C) for backwater temperature and three categories for temperature difference between main channel and backwater (-5 to -1 °C, 0 to +3°C, and +4 to +18°C). Frequency distributions of temperatures of backwaters containing Colorado squawfish were not obviously different from those that did not contain Colorado squawfish. T-tests of backwater temperature between backwaters that contained Colorado squawfish versus those that did not showed significant differences in 6 of the 22 cases examined (Reach 1, 1988 and 1989; Reach 3, 1990; and Reach 4, 1987, 1988, and 1989). All of the significant cases had a warmer mean temperature for backwaters that contained Colorado squawfish than for backwaters that did not; however the difference between the two mean temperatures was small-1.8 to 2.4°C. T-tests compazing temperature differences between main channel and backwaters showed significant differences in only two cases-Reach 1 in 1988 and Reach 4 in 1987. These two cases had temperatures in backwaters containing Colorado squawfish wazmer than the main channel by a lazger amount than the backwaters without Colorado squawfish, but the differences were small-about 1.4°C. ANOVA revealed significant differences in eight cases among the four backwater categories for backwater temperature and in six cases among the three categories of temperature difference. In all cases compazing backwater temperature, the highest catch rate occurred in either the 20 to 23°C category or the 24 to 32°C category. The one exception occurred in 1986 in Reach 1 when no backwaters in the two warmer categories were sampled. In this case, catch rate was higher in the 16 to 19°C category than in the lowest temperature category. Of the significant cases comparing temperature difference between the backwater and main channel, four cases had higher catch rates in backwaters that were wazmer than the main channel and two cases had higher catch rates in backwaters that were cooler than the main channel. Pearson correlation coefficients between gmean CPE of Colorado squawfish and backwater temperature or temperature difference were generally low and not significant. Three of 21 cases were significant for temperature difference (Reach 2, 1986 [r=.72], Reach 3, 1987 [r=.34]; and Reach 4, 1986 [r=.45]; Table B-10) and 3 were significant for backwater temperature (Reach 2, 1986 [r=.72]; Reach 3, 1987 [r=.41]; and Reach 4, 1987 [r=.39]. The significant cases showed a positive relationship between temperature and catch rate, but many of the other cases exhibited negative relationships between the two variables. ~~p~tric Species All fish collected in a seine haul were counted in about 25% of all seine efforts (first seine haul in primazy backwaters). Red shiner, fathead minnow, and sand shiner were the most common species collected in these samples (Figure 7; Tables B-11-B-14). These three species combined composed from 68 to 99% of all species collected from seine hauls where all fish were counted (22 of 28 observations were greater than 90%). Red shiner was overwhelmingly the most common species collected in the Green River (60 to 95% in Reach 3 and 57 to 85% in Reach 4). Fathead minnow was generally second in abundance (2 to 25 % in Reach 3 and 8 to 31 % in Reach 4) and sand shiner was third (0.2 to 12%). Fathead minnow and red shiner were more evenly represented in the catch from the Colorado River. Fathead minnow was typically most common in Reach 2 (42 to 69%) and 16