Physiological Responses of a Native and an Introduced Desert Fish to Environmental Stressors

Abstract

We compared the physiological responses of two similar cyprinids, the Mojave tui chub (Gila bicolor mohavensis) and the arroyo chub (Gila orcutti), to stressors common in their aquatic desert environment. The introduced arroyo chub has displaced the native Mojave tui chub from its fluctuating habitat, a desert river. In laboratory tests, the introduced species showed more appropriate resting—routine metabolic rate responses to increasing temperature and decreasing oxygen tension and better swimming performance responses to high water velocity conditions periodically typical of this habitat than did the native species. This result was expected as the introduced species has a longer evolutionary history in fluctuating stream habitats than does the native species. We concluded that these differences in adaptation contributed to replacement of Mojave tui chub by arroyo chub.