Non-native Fish Control Downstream from Glen Canyon Dam. Environmental Assessment

摘要

The Bureau of Reclamation (Reclamation), Upper Colorado Region, proposes to conduct research, monitoring and specific actions to control non-native fish in the Colorado River downstream from Glen Canyon Dam in an effort to help conserve native fish. The non-native fish control efforts would be located within Glen Canyon National Recreation Area (GCNRA) and Grand Canyon National Park (GCNP), Coconino County, Arizona. The purpose of the action is to minimize the negative impacts of competition and predation on an endangered fish, the humpback chub (Gila cypha) in Grand Canyon. The action is needed because competition and predation by non-native fishes, and in particular rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta), may be contributing to a reduction in survival and recruitment of young humpback chub and threatening the potential recovery of the species. Rainbow trout and brown trout are not native to the Colorado River Basin and have been introduced into the region as sport fish. The action also addresses the concerns of American Indian tribes over the taking of life associated with non-native fish control. Because non-native fish, particularly rainbow and brown trout, are known to prey on and compete with the endangered humpback chub, the U.S. Fish and Wildlife Service (USFWS) 2008 Final Biological Opinion on the Operation of Glen Canyon Dam (2008 Opinion; U.S. Fish and Wildlife Service 2008) included a conservation measure that addressed non-native fish control. That conservation measure provided that Reclamation would continue non-native fish control efforts through the Glen Canyon Dam Adaptive Management Program (GCDAMP) and anticipated removal of non-native trout at the confluence of the Colorado River mainstem and the Little Colorado River (LCR), as well as other control methods. The conservation measure was further guided by the USFWS 2009 Supplement to the 2008 Final Biological Opinion on the Operation of Glen Canyon Dam (2009 Supplement; U.S. Fish and Wildlife Service 2009) and the 2010 Reissuance of the Incidental Take Statement on the 2009 Supplemental Biological Opinion on the Operation of Glen Canyon Dam 2008-2012 (2010 ITS; U.S. Fish and Wildlife Service 2010a).