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Last modified
7/14/2009 5:02:33 PM
Creation date
5/17/2009 11:48:51 PM
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UCREFRP
UCREFRP Catalog Number
8123
Author
Wydoski, R. S.
Title
Coordinated Hatchery Facility Plan
USFW Year
1994.
USFW - Doc Type
Need for Captive-Reared Endangered Fish and Propagation Facilities.
Copyright Material
NO
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r <br />V. STATUS AND TRENDS OF PRESUMPTIVE STOCKS OF ENDANGERED FISHES I <br />A. Stock Identification and Characterization (Genetics Surveys). <br />"Presumptive stock" is used to differentiate aggregations of endangered <br />fish mentioned in this plan. Without genetics data, stock identification <br />and differentiation is based on fish behavior associated with homing or <br />fidelity, verified spawning sites, and geographical separation (Table 1). <br />Criteria involving distribution, behavior, phenotypes, and genotypes of <br />fish aggregations should be considered together in the identification of <br />fish stocks (Dizon et al. 1992). Only rarely are animals distributed <br />randomly. Therefore, disjunct subpopulations must also be analyzed by the <br />amount of gene flow between them (Barker 1989). <br />Fish and wildlife managers can use measures of genetic diversity to <br />determine the contribution of each biological unit (i.e., presumptive <br />stock) to overall biodiversity (Smith and Rhodes 1992). Although <br />researchers have identified presumptive stocks of the endangered fishes <br />based on identified spawning sites or geographical separation, some <br />uncertainties still exist in accurate characterization of these stocks. <br />Presently, contractors are conducting genetics studies that should be <br />helpful in stock identification. Allozyme and nuclear deoxyribonucleic <br />acid (DNA) analyses are being made on presumptive stocks of Colorado <br />squawfish. In addition, allozyme and mitochondrial DNA analyses are being <br />made on presumptive stocks of the razorback sucker. The genetics surveys <br />on the Colorado squawfish and razorback suckers are planned to be <br />completed in 1994. Genetics and systematic analyses of fishes in the <br />genus Gila include morphological studies in addition to allozyme and <br />mitochondrial DNA analyses. The Gila studies are planned to be summarized <br />in an interim report in 1995. The final report is scheduled for March <br />1997. <br />Until the results of the genetics surveys on the endangered fishes are <br />completed and evaluated, a conservative approach was used to identify <br />presumptive stocks of endangered fishes in the Upper Colorado River Basin <br />to ensure retaining the genetic diversity of all possible stocks. Meffe <br />(1986) urged fishery biologists to become more aware of conservation <br />genetics and emphasized that a "conservative approach" be used in managing <br />native fish populations to maintain genetic diversity. <br />Current knowledge of identified spawning sites, geographical separation, <br />and known interchange between stocks were used to differentiate four <br />stocks of razorback suckers, five.stocks of humpback chub, and five stocks <br />of Colorado squawfish in the Upper Colorado River Basin (Table 1). <br />B. Introgressive Hybridization Among Colorado River Fishes. Introgressive <br />hybridization has important management and evolutionary consequences and <br />increases when ailopatric species are placed into sympatry through human <br />activities and when sympatric species inhabit altered environments (Buth <br />et al. 1987). The frequency of introgressive hybridization of razorback <br />suckers with flannelmouth suckers (Catostomus latipinnis) is low (0 - 5% <br />toward flannelmouth suckers; Buth et al. 1987) but may increase if the <br />riverine environment in the upper basin is altered further, forcing the <br />two species to spawn on the same area. <br />12
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