What environmental factors reduce predation vulnerability for native fishes?

Authors: Tammy L. Knecht, David L. Ward

Year: 2012 (xliv)

Abstract

The incompatibility of native Colorado River fishes and nonnative warm water fishes is well documented with predation by nonnative species causing rapid extirpation of native species in most locations. In a few rare instances native fishes are able to survive and recruit despite the presence of nonnative warm water fishes, indicating that specific environmental conditions may help reduce predation vulnerability. We experimented with turbidity, artificial water colorant, woody debris, aquatic vegetation, or rock substrates in a laboratory setting to determine if any of these types of cover could reduce predation vulnerability and confer survival advantages for juvenile bonytail chub, Gila elegans. Bonytail chub were exposed to predation by adult largemouth bass, Micropterus salmoides, or green sunfish, Lepomis cyanellus, in overnight trials. Turbidity above 1,000 NTU reduced predation vulnerability by up to 50 percent, with no other treatment significantly reducing predation mortality. If our results can be extended to other species, they may help to explain patterns of wild juvenile razorback sucker, Xyrauchen texanus, recruitment at the turbid inflow of the Colorado River into Lake Mead.