Effect of Brook Trout Removal from a Spawning Stream on an Adfluvial Population of Lahontan Cutthroat Trout

Abstract

Independence Lake (Nevada and Sierra counties, California) harbors the only extant native population of Lahontan cutthroat trout Oncorhynchus clarkii henshawi in the Truckee River system and one of two extant adfluvial populations in the Lahontan basin. The persistence of this population has been precarious for more than 50 years, with spawning runs consisting of only 30–150 fish. It is assumed that this population was much larger prior to the introduction of nonnative brook trout Salvelinus fontinalis. Brook trout overlap with cutthroat trout in upper Independence Creek, where the cutthroat trout spawn and their resulting progeny emigrate to Independence Lake. In 2005, we began removing brook trout from upper Independence Creek using electrofishers and monitored the cutthroat trout population. Stomach analysis of captured brook trout revealed cutthroat trout fry, and cutthroat trout fry survival increased significantly from 4% to 12% with brook trout removal. Prior to brook trout removal, the only Lahontan cutthroat trout progeny emigrating to Independence Lake were fry; with brook trout removal, juveniles were found entering the lake. In 2010, 237 potential spawners passed a prefabricated weir upstream of Independence Lake. Although the results of this study suggest that brook trout removal from upper Independence Creek has had a positive influence on the population dynamics of Independence Lake Lahontan cutthroat trout, additional years of removal are needed to assess the ultimate effect this action will have upon the cutthroat trout population.Received August 26, 2011; accepted February 29, 2012

Assessing thermal adaptation using family‐based association andFSToutlier tests in a threatened trout species

“…Independence Lake is within the same watershed as Pyramid Lake, but is relatively distinct based on these SNPs and other neutral genetic markers (e.g., microsatellites; Peacock et al, ). Recruitment into the Independence Lake LCT population has been decimated by the presence of non‐native brook trout ( Salvelinus confluentus ) over the last few decades (Scoppettone, Rissler, Shea, & Somer, ), which probably contributed to drift (given low N e ) in this population. The amount of genetic variability retained in the modern Pilot Peak broodstock is also certainly reduced compared to the historical Pyramid Lake population.…”