Ecology of Bonytail and Razorback Sucker and the Role of Off-Channel Habitats in Their Recovery - Usgs Scientific Investigations Report 2006-5065 (Paperback)

The bonytail and razorback sucker are two of four endangered mainstem fishes found in the Colorado River. Unlike the Colorado pikeminnow and humpback chub, wild populations of the bonytail and razorback sucker are either extirpated from the mainstem river or are nearly so. Agencies are aggressively stocking these fish wile repatriated fish spawn, their young are rapidly eaten by introduced predators. A decade of predator removal efforts has proved ineffective in restoring natural recruitment. Today, the presence of these species is totally dependent on stocking, suggesting both species are worse off today than when recovery efforts began nearly two decades ago. In contrast, both species readily produce young in ponds where nonnative predators are absent. Evidence shows they evolved with the ability to spawn in both flowing and standing water, which suggests isolated oxbow communities may be been an essential feature in their evolution and survival strategy. Sustainable populations during the past few decades have only occurred in isolated ponds devoid of predatory nonnative fish. Efforts to force recovery in the main channel river continue to fail due to the presence of nonnative predators that may be economically important recreational species. Off-channel sanctuaries provide research and management opportunities on a scale that are both biologically and economically realistic.