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<br />Squawfish Population Viability Analysis --July 1993 <br /> <br />Page 13 <br /> <br />1.11 Adult Growth Rates <br /> <br />One finds different estimates of adult growth rates. Tyus (1991) estimates <br />11 mmlyear. Hawkins (1991), based partially on scale ring analysis, <br />arrives at figures in the 30 to 50 mm1year range. And Nessler (1992) <br />implicitly assumes something in the range of 50 mmlyear. The figure <br />below is based on the 1400 record CRFP database. Growth rates based on <br />recaptures of at least a full season's length are plotted against length in <br />Figure 1.5. Note that the regression explains only 14% of the variation. <br /> <br /> 70 Y = .018x + 2.211, r 2 = .014 <br /> 60 0 <br /> 50 o GcRate/yr <br /> 40 0 0 00 <br />~ 00 o 0 0 0 <br />- 30 0 <br />B 0 00 <br />~ <br />P:::I 20 ---__.9_~ <br />.... <br />0 10 <br /> --- <br /> 0 --- <br /> <br />-10 0 <br /> <br />-20 <br />350 400 450 500 550 600 650 700 750 800 850 900 <br />Length (mm) <br /> <br /> <br />o <br /> <br />o <br /> <br />Figure 1.5 <br /> <br />These data indicate a growth rate in the range of 10 to 15 mm per year. <br />There is a suggestion that slightly higher absolute growth rates occur for <br />larger fish (this is, of course, a lower percentage rate of growth). <br />Importantly, there is a lot of variation in adult growth, probably reflecting <br />chance factors of different types. Negative length growth is probably due <br />to measurement error. <br /> <br />1.12 A Full Life Table Model <br /> <br />To build a Leslie Matrix model for the Colorado Squawfish of the form <br />mentioned earlier in this report, one has to first decide upon a time step <br />and a date of observation. Much mischief and misunderstanding can result <br />