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<br />002837 <br /> <br />or 3-3.4/mile in the Utah reach below Westwater Canyon, Their assessment of the status ofthis <br />population was that the low numbers of Colorado squawfish adults estimated are likely the result <br />of insufficient reproductive success and recruitment during most years, that production of strong <br />year classes to sustain adult abundance is more infrequent now than historically, and that the <br />estimated abundance level was below the theoretical effective population' size threshold to <br />maintain genetic viability, The authors indicated this population was vulnerable to extinction <br />due to stochastic demographic fluctuations. Osmundson et al, (1996) estimated a 0.86 survival <br />rate for the existing population. Osmundson and Burnham (1996) suggest a 4% increase in <br />survival while holding recruitment steady, or a 4 % increase in recruitment while holding <br />survival steady would result in a doubling of population size in 18 years, An objective of <br />stocking Colorado squawfish is to produce an increase in recruitment in the Colorado River and <br />Gunnison River populations in the short term, while other recovery actions target improvement <br />of survival and recruitment of this species to preclude the need for augmentation in the long <br />term. <br /> <br />This review and evaluation of population status and recruitment potential for the Grand <br />Valley population of Colorado squawfish identifies considerable uncertainty in the efficacy of <br />depending upon natural recolonization of the target unoccupied reaches of the upper Colorado <br />and Gunnison by the existing adult population, or using the Grand Valley adult population as a <br />donor for trans locating sufficient numbers of fish above the instream barriers in one or both <br />unoccupied reaches to create an effective population size in a timely manner. Translocation <br />raises additional risk issues concerning: <br /> <br />1) Reproductive success of translocated fish taken from a home range cannot be <br />assumed to be the same in the new environment for a species with a complex <br />spawning behavior. <br />2) the complex reproductive cycle of this species, including factors of imprinting, <br />chemoreception, learned behavior, or other instinctual behaviors are not <br />understood. <br /> <br />DRAFT - June 4, 1997 <br /> <br />13 <br />