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P <br />D <br />P <br />9 <br />D <br />(flannelmouth and bluehead sucker) and non-native (white sucker) <br />members of the catostomid family. This has two important <br />consequences--loss of interpopulational genetic identity and <br />perhaps outbreeding depression, i. e., reduced fitness. <br />Flannelmouth X razorback sucker hybrids have been observed in <br />nature throughout the Colorado River basin for almost 100 years <br />(Jordan 1891; Vanicek et al. 1970; Holden and Stalnaker 1975; <br />McAda and Wydoski 1980; Carothers and Minckley 1981; Buth et al. <br />1987), but the rate of hybridization reported in these accounts <br />appears to be low. However, it is difficult to determine whether <br />the incidence of hybridization has increased or decreased during <br />this period. Early investigators used traditional taxonomic and <br />systematic methods (e. g., morphometric and meristic characters) <br />to make their classifications. In addition to traditional <br />methods, modern taxonomic studies utilize more sophisticated <br />techniques (e. g., electrophoresis, cytogenetics, or mitochondrial <br />DNA) to determine whether razorback sucker hybridize with other <br />catostomids. Stocking hatchery-reared razorback sucker would not <br />be expected to increase the hybridization rate in the wild. <br />Indirect Risks <br />1. Pathogen and Parasite Transmission: pathogens and parasites <br />harbored by artificially-produced fish could adversely impact wild <br />native fish populations. Specifically, a resistant stock may <br />carry pathogens into populations with little or no resistance. <br />2. Intra- and interspecific competition: hatchery-produced fish could <br />compete directly for food and space with native fish. <br />13 <br />B