SGER: Biodiversity of Native Mexican Trout (Genus Oncorhynchus spp.) and The Impending Treat of Their Demise by The Exotic Rainbow Trout O. mykiss gairdneri (Teleostei: Salmonidae)

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A grant has been awarded to Dr. Richard L. Mayden at Saint Louis University to conduct field and laboratory research in collaboration with other USA scientists and several scientists from Mexico on the environmental status, distribution, conservation and genetics of native trout populations of Mexico. While biologists have been aware of the existence of native trout in Mexico for over a century, they have received little study. Beginning in the mid-1990's a group of ichthyologists and conservation biologists from both Mexico and USA jointly formed an international alliance, Truchas Mexicanas, to better understand the native trout of the Sierra Madre Occidental. Through these efforts, scientists have discovered previously unknown trout species restricted to Mexico and introduced (non-native) populations of rainbow trout. The existence of these non-native rainbow trout originating from streams in the US and Canada in the ranges of the unique Mexican trout species is a significant threat to the future existence of native species. Rainbow trout are known to displace native trout species through competition or genetically "swamp out" their gene pools through aggressive hybridization. Other native populations of trout are also predicted to occur in the upper Rio Conchos; these populations are predicted to also be in danger from habitat destruction and introductions of rainbow trout. In this study we will inventory many river systems of the sierras for native and introduced trout species, including the upper Conchos River system. Genetic samples will be examined from all of these populations to evaluate genetic variability of native species and determine if any native populations are compromised genetically through hybridization with introduced rainbow trout. This research supports the development of an international alliance investigating native trout populations of Mexico and southwestern United States. Trout species are important game and forage species for human populations, constituting a major element of diets in some regions. Trout fisheries are also very important economic elements to some regions as trout are highly prized sport fish species. Understanding native trout species diversity in Mexico and its conservation and maintenance in these streams has a major impact on both fisheries and economic areas. Mexican trout species are the southern-most trout and are adapted to theses unique ecosystems. Introductions of non-native rainbow trouts will seriously jeopardize these adapted populations and lead to their extirpation from the region. This will have serious sociological and economic impacts for the native people of the region.