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Last modified
1/26/2010 4:18:45 PM
Creation date
10/22/2007 8:15:19 AM
Metadata
Fields
Template:
Water Supply Protection
File Number
8240.200.10.H
Description
Upper Colorado River Endangered Fish Program
Basin
Colorado Mainstem
Date
10/15/2001
Author
Thomas P. Nesler CDOW
Title
Stocking Plan for Endangered Colorado River Fish Species in Colorado
Water Supply Pro - Doc Type
Publication
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<br />12 <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />used will receive implanted, unique PIT tags, and selection criteria for paired matings includes <br />only no duplicat~' use of any adult fish used in previous matings. This strategy using wild <br />Colorado pikeminnow from the Colorado and Gunnison Rivers is logical and appropriate given <br />the availability of wild adult fish and priorities based on available fish according to the genetics <br />management guidelines. Using this strategy, the genetics risks associated with production of <br />progeny for restoration stocking are negligible. The risk assessment targets two issues: (1) the <br />genetic impacts of restoration stocking of hatchery-reared fish in river reaches located upstream <br />of occupied habitat compared to natural or enhanced (via translocation) recolonization of habitat <br />by passage of fish past barriers with little or no genetic impact, and (2) movement of stocked fish <br />downstream into reaches occupied by wild Colorado pikeminnow. <br /> <br />Osmundson and Burnham (1996) estimated the population size of Colorado pikeminnow <br />in the Grand Valle:r reach of the Colorado River to be about 250 fish or 4/mile, and 340-390 fish <br />or 3-3.4/mile in the Utah reach below Westwater Canyon. Their assessment of the status of this <br />population was low numbers of Colorado pikeminnow adults are likely the result of insufficient <br />reproductive succe:;s and recruitment during most years, that production of strong year classes to <br />sustain adult abundance is more infrequent now than historically, and the estimated abundance <br />level was below the theoretical effective population size threshold to maintain genetic viability. <br />The authors indicated this population was vulnerable to extinction due to stochastic demographic <br />fluctuations. Osmundson et al. (1996) estimated a 0.86 survival rate for the existing population. <br />Osmundson and Burnham suggest a 4 % increase in survival while holding recruitment steady, or <br />a 4% increase in recruitment while holding survival steady would result in a doubling of <br />population size in 18 years. <br /> <br />This review and evaluation of population status and recruitment potential for the Grand <br />Valiey population of Colorado pikeminnow does not lend much support for the efficacy of <br />depending upon natural recolonization of the target unoccupied reaches of the upper Colorado and <br />Gunnison by the e}isting adult population, or using the Grand Valley adult population as a donor <br />for translocating sufficient numbers of fish above the instream barriers in one or both reaches to <br />create an effective population size in a timely manner. Translocation raises concern over <br />additional risks that include: <br /> <br />1) reproductive success of translocated adult fish taken from a home range; it cannot be <br />assumed to be the same in the new environment for a species with a complex spawning <br />behavior. . (Conversely, the expectation of reproductive success in stocked populations must <br />also be tested through monitoring.) <br /> <br />2) the complex reproductive cycle of this species, including factors of imprinting, <br />chemoreception, learned behavior, or other instinctual behaviors are not understood. <br /> <br />3) reproductive tradeoffs cannot be assumed equal or insignificant between established <br />patterns in Grand Valley sites and new sites upriver with respect to spawning behavior, <br />spawning !Uccess, hatching success, and larval and young-of-the-year survival. <br />
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