Relationship between stream and lake ecotypes of Warner suckers

Authors: Patrick* DeHaan, Jennifer Von Bargen, Paul Scheerer

Year: 2015 (xlvii)

Abstract

The Warner sucker, Catostomus warnerensis, is endemic to the Warner Valley, an endorheic subbasin of the Great Basin in southeastern Oregon. Two distinct ecotypes of Warner suckers exist; stream-type fish that are found in tributaries to the Warner Lakes and lake-type fish that are found in Hart and Crump Lakes. Lake-type fish attain larger sizes and presumably have increased fecundity, but risk increased predation, reduced access to spawning habitat, and periodic loss of habitat due to lake desiccation. Stream-type individuals inhabit a more stable environment with reduced risk of predation, however, they have a decreased forage base and stream habitat in the Warner basin has been extensively fragmented. Although it is presumed that lake-type individuals originate in the streams, information regarding the relationship between the two ecotypes is limited. Our objective was to use genetic assignment data to examine the relationship between the two ecotypes. We collected Warner suckers from four tributary populations and genotyped them at 16 microsatellite loci to develop a baseline dataset. Leave-one-out tests of our baseline dataset indicated a high likelihood that individuals from the lakes would be assigned to their correct population of origin. Between 2006 and 2012, we collected over 300 individuals from Hart and Crump lakes for genetic assignments and these fish were also genotyped at 16 microsatellite loci. Nearly all of the individuals collected from Crump Lake were assigned to Deep Creek, a tributary to Crump Lake. Individuals collected from Hart Lake were assigned to both Deep Creek and Honey Creek (a Hart Lake tributary), suggesting that fish were moving between the two lakes. These data provide important information regarding which tributary populations are important to Warner suckers in the lakes and will help to prioritize management actions such as increasing connectivity between lake and stream populations.