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<br />. <br /> <br />. <br /> <br />2 <br /> <br />o Humpback chub: <br />-Adult humpbacks can be sampled relatively effectively and the <br />size of their populations can be estimated, <br />-Young and juvenile humpbacks cannot be sampled effectively_ <br />-The age-class structure of the population can be estimated based <br />on length-frequency data, However. older year classes are harder <br />to differentiate by this method as growth rates decrease with age_ <br /> <br />o Razorback suckers and Bony tail : <br />-Only hatchery-stocked fish are currently found in the Colorado <br />River subbasin. It will take 7-15 years to determine if stocked <br />fish reproduce and contribute to the establishment of a wild <br />population, <br /> <br />Proposed Approach <br /> <br />population Indicators <br /> <br />Based on the above limitations/realities, the following indices were selected <br />to assess the status of or trends in the endangered fish populations: <br /> <br />o Colorado pikeminnow <br />-size of the wild adult Colorado pikeminnow population based on <br />surveys of the adult population; <br />-structure of the adult population as determined by the length- <br />frequency distribution of wild adults; <br />-annual production of Colorado pikeminnow based on the capture of <br />wild YOY fish each fall; <br /> <br />o Humpback Chub <br />-structure of the adult humpback chub population as determined by <br />the length-frequency distribution of wild adult humpback chub; <br />-size of the wild adult humpback chub population (when these <br />estimates are finalized); <br /> <br />o Razorbacks and Bony tails <br />-Colorado pikeminnow and humpback chub will serve as surrogates <br />for razorback suckers and bony tails to assess the status of their <br />populations for 10 years or until self-sustaining populations of <br />razorbacks and bony tails are re-established. Goals/expectations <br />for razorbacks and bony tails will be established by December 1999 <br />based on implementation of recovery actions (e.g., propagation and <br />