Status, Distribution, and Movement of the Warner Sucker in the Desert of Southeastern Oregon

Abstract Warner Sucker (Catostomus warnerensis), endemic to the lakes and tributaries of the Warner basin, southeastern Oregon, USA, was listed as threatened by the US Fish and Wildlife Service in 1985 because of habitat fragmentation and threats from introduced nonnative fish. To determine progress towards recovery and document factors that may prevent recovery, we evaluated the distribution, abundance, and movements of this species between 2006 and 2013. The species exhibits 2 distinct life-history types, a lake morph and a stream morph. The abundance of suckers in the Warner Valley lakes has decreased since the mid-1990s, and the lake fish assemblages were dominated by nonnative predatory fishes. The basin experienced drought conditions from 2007 through 2010, and the lakes partially dried which affected both sucker distribution and movement. During the drought, when lake levels were low and receding, we found little evidence of sucker recruitment in the lake populations. In 2011, stream discharge was ...