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<br />1366 <br /> <br />BESTGEN ET AL, <br /> <br />TABLE 4,-Abundance estimates, 95% confidence intervals (CIs), coefficients of variation (CVs), numbers of unique <br />individuals captured (M,+l) and percentages of recruits for Colorado pikeminnow in the Green River basin, Utah and Colorado, <br />2000-2003, Percent recruits is the abundance of recruits (400-449 mm TL) relative to that of adults (;::450 mm) in the same year <br />multiplied by 100, Two estimates of adult abundance are shown for 2000, The fust is for the middle Green, Yampa, and White <br />River reaches only; the second includes estimates for the Desolation-Gray Canyon (N = 699) and lower Green River (N = 355) <br />reaches in 2001 to account for the lack of sampling in those areas in 2000, The estimate for recruits in 2000 includes only the <br />middle Green, White, and Yampa river reaches. An estimates for 2001-2003 include those areas and the Desolation-Gray <br />Canyon and lower Green River reaches. <br /> <br />Adult <br /> <br />% Recruits <br /> <br />Year Abundance SE 95% CI CV Mt+1 <br />2000 3,030 286,8 2,467-3,592 9 910 <br />2000 4,084 <br />2001 3,304 206.1 2,900-3,707 6 990 <br />2002 2,771 282,7 2,216-3,325 10 455 <br />2003 2,142 232,7 1,686-2,598 11 434 <br />2000 150 26,3 98-201 18 39 <br />2001 4]2 51.1 312-512 12 105 <br />2002 130 35,5 61-200 27 17 <br />2003 284 55,8 175-393 20 43 <br /> <br />Life stage <br /> <br />Recruit <br /> <br />4,9 <br />12.5 <br />4,7 <br />13.3 <br /> <br />the number of adults present in any given year. <br />Estimates of Colorado pikeminnow recruit abundance <br />were significantly higher in 2001 than in 2000 or 2002 <br />but showed no consistent trend over the sampling <br />period; CVs ranged from 12% to 27%, <br /> <br />Survival Estimates <br /> <br />The best model suggested a constant survival rate (S) <br />over the study period (Figure 4) with the terms TL, <br />TL2, and TL3. The parameters for the function of logit <br />S are as follows: intercept = 0.6173 (SE = 0.1370), TL <br />=0.5606 (0.2373), TL2=-0.2068 (0.1140), and TL3= <br />-0,1320 (0.0665). Survival was relatively low for fish <br />about 350 mm TL, increased for fish up to about 600 <br />mm, and then declined for larger fish, The average S <br />adjusted to the mean TL for Colorado pikeminnow <br />across all river reaches was 0.65 (95% confidence <br /> <br />-- 2000-2003 -1991-1999 <br /> <br /> <br /> 0.8 <br />';;j 0,6 <br />;> <br />';;C <br />... <br />::l 0.4 <br />Vl <br /> 0.2 <br /> 0 <br /> 300 400 500 600 700 800 900 <br /> <br />Colorado pikeminnow TL <br /> <br />FiGURE 4.-Survival rate of Colorado pikeminnow as a <br />function of TL (mm) in the Green River basin in 1991-1999 <br />and 2000-2003, The 1991-1999 data were collected during <br />Interagency Standardized Monitoring Program (ISMP) sam- <br />pling; data from other periods were collected during <br />abundance estimation sampling, <br /> <br />interval [CI] , 0,586-0.708) for the 2000-2003 study <br />period (Table 5). <br />The average S for Colorado pikeminnow captured <br />during ISMP sampling from 1991 to 1999 was 0.82 <br />(95% CI, 0.709-0.891), which was higher than that <br />observed for 2000-2003. The shape of the survival <br />relationship was also different, as the best-fit model <br />included a linear term for the covariate fish TL but not <br />a quadratic term. An exploratory analysis revealed that <br />a quadratic term had a positive coefficient, indicating <br />that the slope continued to rise rather than to decline, <br />unlike the survival relationship for the 2000-2003 data. <br />The mean probabilities of capture for the fish used in <br />the above survival analyses were higher in 2000-2003 <br />than in 1991-1999. <br /> <br />Probabilities of Capture <br /> <br />The capture probabilities for Colorado pikeminnow <br />generated from abundance estimation data also dem- <br /> <br />TABLE 5.-Estimates of apparent sUlvival and capture <br />probability and 95% confidence intervals (CIs) for subadult <br />and adult Colorado pikeminnow captured in the Green River <br />basin in 1991-1999 and 2000-2003, The data for 1991-1999 <br />were collected as part of a standardized monitoring program to <br />estimate catch per unit effort indices for Colorado pike- <br />minnow and were from about 23% of the habitats occupied by <br />this species in the Green River basin, The data for 2000-2003 <br />were collected during this study to estimate the abundance of <br />subadult and adult Colorado pikeminnow throughout the <br />Green River basin; the data for 2000-2001 were from the <br />middle Green, Yampa, and White river reaches only, <br /> <br />Variable Period Estimate 95% C1 <br />Survival 1991-1999 0,82 0,709-0,891 <br /> 2000-2003 0,65 0,586-0,708 <br />Capture probability 1991-1999 0.053 0.038-0.074 <br /> 2000-2003 0,090 0,054-0,119 <br />