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<br />694 <br /> <br />0.6 <br /> <br />OSMUNDSON ET AL. <br /> <br />0.5 <br /> <br /> <br />Q) 0.4 <br />~ <br />ctS 0.3 <br />~ <br />"'C 0.2 <br /> 0.1 <br /> <br />o <br />0.6 0.7 0.8 0.9 <br />Survival rate (fraction) <br /> <br />FIGURE 6.-Kolmogorov-Smirnov D-statistic for test <br />between stable size distributions and measured size dis- <br />tributions for Colorado squawfish 550 mm TL and longer <br />captured during 1991-1994. Dotted Jines represent <br />maximum d-value (D-statistic) for P = 0.001 and P = <br />0.05. Lesser d-values have lower significance levels. Ex- <br />amples of observed and theoretical length distributions <br />of three survival rates and associated statistics are in <br />Figure 7. <br /> <br />Discussion <br /> <br />Growth, Age, and Size <br /> <br />As expected, our estimates of growth rates and <br />mean lengths by age-class were similar to those <br />based on scale analyses reported by Seetha1er <br />(1978) and Hawkins (1992) up to ages 8-10 (Fig- <br />ure 3), given that our analyses through age 7 was <br />also based on scales. Mean lengths at a given age <br />were nearest to those of Seethaler (1978), though <br />his estimates were slightly lower. This may reflect <br />differences in the annual reference point: mid win- <br />ter for Seethaler and mid to late spring for this <br />study. A 130C threshold in water temperature for <br />Colorado squawfish growth (Osmupdson 1987; <br />Kaeding and Osmundson 1988) is attained in our <br />study area in March or April, providing 1-3 <br />months of additional growth for fish measured in <br />mid-April to late June compared with estimated <br />lengths at annulus formation in midwinter. <br />Results of scale analysis and additive recapture <br />increments diverge after fish are 10 years old. <br />Seethaler's (1978) and Hawkins' (1992) scale- <br />based Colorado River results ended at ages 11 and <br />12, respectively; however, the latter's pooled data <br />from upper-basin rivers continued through age 18. <br />All earlier curves indicated high and relatively <br />constant growth rates through the last years ex- <br />amined, whereas our estimated rates are lower af- <br /> <br /> 50 <br /> 40 <br /> 30 <br /> 20 <br /> 10 <br /> 0 <br />- 50 <br />~ <br />0 <br />.......... 40 <br />~ 30 <br />C <br />CD <br />::J 20 <br />CT <br />CD 10 <br />"- <br />LL <br /> 0 <br /> 50 <br /> 40 <br /> 30 <br /> 20 <br /> 10 <br /> <br /> <br />A <br /> <br />s = 0.81 <br />d = 0.132 <br />P = 0.0080 <br /> <br />8 <br /> <br />s = 0.86 <br />d = 0.051 <br />p= 0.814 <br /> <br /> <br />c <br /> <br />s = 0.91 <br />d = 0.168 <br />P = 0.0003 <br /> <br /> <br />o <br />550-599 650-699 750-799 850-899 <br />600-649 700-749 800-849 900-949 <br /> <br />Total length (mm) <br /> <br />FIGURE 7.-Stable length distributions (black) and <br />measured length distributions (white) during 1991-1994 <br />for Colorado squawfish. Graphs show stable length dis- <br />tributions assuming survival rates (s) of (A) 0.80; (B) <br />0.85; and (C) 0.90. Maximum d-values from Kolmo- <br />gorov-Smirnov one-sample tests and associated prob- <br />ability levels (P) are shown. <br /> <br />ter fish attain about 550 mm (Figure 3). We concur <br />with Hawkins' (1992) caution that scale-based es- <br />timations are probably unreliable for Colorado <br />squawfish beyond about age 10. <br />Our estimates of mean annual increments from <br />tagged and recaptured adults are similar to reports <br />by others. Tyus (1988) recorded an average gain <br />of 10.2 mm (SD = 11.3 mm) in length per year <br />for recaptured adults (N = 59; 482-770 mm TL) <br /> <br />.. <br />