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<br />Squawfish Population Viability Analysis --July 1993 <br /> <br />Page 42 <br /> <br />How long a river reach is required to sustain the Colorado squawfish? <br />Judging from the stretches where the Colorado squawfish has gone extinct, <br />above and below major reservoirs, something in the range of 200 miles is <br />probably minimal. This hypothesis could be tested if one built a dam at <br />about river mile 80 on the Green River. <br /> <br />Originally <br /> <br />..... spawning and <br />~. transport of fry adults <br />progeny ~ <br /> <br />_ '--- ~ ~~ruits <br /> <br />down stream up stream <br /> <br />Reduction in Length of River <br /> <br />..... spawning and <br />~transport of fry adults <br />progen)j _ IS... <br /> <br />__ '--- ~ ~ recruits <br /> <br />down stream up stream <br /> <br />Figure 4.2. In the original configuration of the river, the number of <br />recruits to the adult population is sufficient to maintain local number. <br />After the river is shortened, some of the juveniles are lost (the stippled <br />area), and thus the recruitment is lower. At some degree of shortening the <br />number of recruits falls below replacement level. This illustrates the <br />operation of the computer model MVLength. <br /> <br />4.5 Spatial Effects and Colorado Squawfish Recovery <br /> <br />Because of limited data and virtually no purposeful experimentation, it is <br />impossible to reach firm conclusions about the role of space in Colorado <br />