Riparian Habitat Restoration and Native Southwestern USA Fish Assemblages: A Tale of Two Rivers

摘要

In the southwestern United States, livestock grazing has occurred on the landscapes for over a century. Because of aridity of climate and frequent drought, domestic livestock often resort to wetlands and riparian stream corridors for forage and water.One argument against this type of land use is the indirect impact on native fish species, many threatened and endangered within these aquatic habitats. Removal and reduction of livestock to improve and restore riparian vegetative habitat has been a management alternative that has been implemented across a large proportion of streams in the southwestern United States. We present data on two river systems, the Gila and the Verde, from which livestock have been removed for similar periods of time. Fish assemblages in these "improved" riparian areas have responded in two markedly different manners. In one, introduced species of fishes are now dominant. In the other, native fishes dominate fish assemblages. We compare physical habitat data and fish assemblages in these two rivers. We submit that overriding, natural hydrologic influences are perhaps more important in terms of habitat essential for sustaining fishes assemblages than is simple increase in riparian vegetation that may result from riparian restoration activities.