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<br />OTOLITH MICROSTRUCTURE OF COLORADO SQUAWFISH
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<br />109
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<br />TABLE 2.-Least-squares statistics for otolith increment count (IC) as a function of days since hatching (known age)
<br />for Colorado squawfish incubated and reared for 165 d with constant temperature (220C) or with diel temperature
<br />fluctuations (:!:2.5OC around 18,22, or 260C), Regressions are IC = a + b (known age), P denotes the significance of
<br />the test of intercept = 0 or slope = I, and CI denotes the 95% confidence interval about the estimate. Prediction limits
<br />were calculated for mean known age. instead of estimated age, via inverse regression.
<br />
<br /> 95% prediction
<br /> limits for known
<br /> age of individual
<br /> Intercept: Slope: larvae (:!:number
<br />Treatment df a (P; CI) b (P; CI) r2 of increments)
<br />180C fluctuating 46 0,019 (0,978; -1.371 to 1.409) 1.019 (0,074; 0,998 to 1.040) 0,995 ::!:7,8
<br />220C fluctuating 41 -0,114 (0,871; -1.514 to 1.287) 0,992 (0.484; 0,970 to 1.014) 0,995 :!:7,1
<br />22"C constant 38 1,409 (0,440; -2.230 to 5,050) 1.003 (0,911; 0,975 to 1.089) 0,972 :!:17.7
<br />26"C fluctuating 54 -0,123 (0,830; -1.261 to 1.016) 0,993 (0,497; 0,971 to 1.014) 0,994 :!:7,1
<br />All fluctuating
<br />treatments combined 143 -0.130 (0,729; -0,873 to 0.612) 1.003 (0,585; 0,991 to 1.015) 0,995 ::!:7.2
<br />All treatments
<br />combined 182 0,178 (0,708; -0,752 to 1.108) 1.004 (0,617; 0.989 to 1.019) 0,989 :!:lO,l
<br />
<br />ments at 220C (constant and fluctuating tempera-
<br />ture) were pooled within reader for this analysis
<br />because no significant differences between treat-
<br />ments were detected (reader 1: P = 0.71 for slopes,
<br />P = 0.18 for intercepts; reader 2: P = 0.94 for
<br />slopes, P = 0.84 for intercepts).
<br />The ANCOV A for regressions of increment
<br />count versus known age for larvae reared at tem-
<br />peratures fluctuating around 18, 22, and 260C in-
<br />dicated no significant temperature effect on daily
<br />increment deposition rates (Table 3). Estimated
<br />means (SE) were 36.7 d (0.61) at l80C, 36.3 d
<br />(0.66) at 220C, and 36.1 d (0.59) at 260C; the dif-
<br />ference between means for 18 and 260C treatments
<br />was 0.6 d (CI, :t: 1.56).
<br />
<br />Temperature versus Otolith Growth
<br />The ANCOV A of otolith diameter as a function
<br />of loge (TL) suggested that slopes of regression
<br />relationships (Table 4) differed significantly among
<br />temperature treatments (F = 7.71, P <0.0001).
<br />Lapillus diameter at hatching (intercepts) and oto-
<br />lith growth (slopes) were similar for fish from 22
<br />and 260C fluctuating treatments. The lower slope
<br />estimate for fish reared at 180C (with fluctuations)
<br />suggested slower otolith growth in that treatment.
<br />The higher intercept at l80C was likely an artifact
<br />of the lower slope estimate, because empirical data
<br />suggested that otolith size at hatching was the same
<br />or slightly smaller for fish in this treatment than
<br />for fish hatched in 22 and 260C treatments.
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<br />TABLE 3.-Analyses of covariance for increment count (estimated age) as a function of true age Of young Colorado
<br />squawfish. The reader comparison (two otolith readers) is for data pooled over constant and fluctuating temperatures
<br />centered on 220C, The temperature comparison (three treatments) is for fluctuating temperatures centered on 18, 22, and
<br />260C. The respective reader and temperature terms are indicator variables, Probability values for the intercept tests are
<br />for differences in means between groups designated by the indicator variable after adjustments were made for the
<br />covariate. The interaction terms test for equivalence of slopes between groups.
<br />
<br />R2
<br />
<br />Effect df Sum of squares F P
<br /> Reader comparison
<br />Slope test
<br />Age 380,250,47 6,579,05 <0,0001
<br />Reader 1.86 1.86 0.86
<br />Age X reader 34,92 34,92 0,44
<br />Intercept test
<br />Age 380,256,10 6,595,47 <0,0001
<br />Reader 45,30 45.30 0,79
<br /> Temperature comparison
<br />Slope test
<br />Age I 311,879.33 16,820,11 <0.001
<br />Temperature 2 3,80 0,10 0,90
<br />Age X temperature 2 2953 0,80 0,45
<br />Intercept test
<br />Age 1 320,021.26 17 ,308,53 <0,001
<br />Temperature 2 7,58 3,79 0,82
<br />
<br />0,98
<br />
<br />0,98
<br />
<br />0.99
<br />
<br />0,99
<br />
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