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Last modified
7/14/2009 5:01:47 PM
Creation date
5/20/2009 11:05:16 AM
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UCREFRP
UCREFRP Catalog Number
8161
Author
Osmundson, D. B., R. J. Ryel and T. E. Mourning.
Title
Growth and Survival of Colorado Squawfish in the Upper Colorado River.
USFW Year
1997.
USFW - Doc Type
\
Copyright Material
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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 />
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