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<br />Squawfish Population Viability Analysis --July 1993 <br /> <br />Page 12 <br /> <br /> 700 <br /> 650 <br /> 600 <br />oS <br />~ 550 <br />.3 <br />~ 500 <br />.... <br />'0 <br />~ 450 <br />~ <br /> 400 <br /> 350 <br /> 300 <br /> 80 81 <br />Figure 1.4 <br /> <br /> <br />o Median Length <br /> <br />82 83 84 85 86 87 88 89 90 <br /> <br />The year 1983 shows more subadults than other years~ this lowers the <br />median age, and it might indicate a strong flush of recruitment into the <br />adult population. Ignoring 1983, the pattern of adult size is quite stable. If <br />adults have, say, average length growth of 30 to 50 mmlyear, and if <br />mortality is independent of size, then one would expect an upward shift of <br />250 to 400 mm over the course of these observations if there were no <br />recruitment of juveniles into the adult distribution. Even a lower adult <br />growth rate of 10 to 15 mm per year should show up in this figure if there <br />were no recruitment. So, again agreeing with Hawkins and with other data <br />(e.g., releases into the Colorado of tagged juveniles, Osmundson, pers. <br />com.) there seems to be ongoing recruitment into the adult population <br />resulting in a quite "stable" distribution of adult sizes. <br /> <br />1.10 Juvenile Growth Rates <br /> <br />There seems to be no disagreement with a view of high juvenile growth, <br />reaching about 460 mm at age 7, the age (or size) of sexual maturity. This <br />is an average growth rate of roughly 50 mm per year~ <br /> <br />In some ways, the exact age-specific juvenile growth and survival are not <br />too important to a demographic analysis, as juveniles can be accounted for <br />in a kind of black box with a seven year delay until they show up as adults. <br />