title: High thermal tolerance of a rainbow trout population near its southern range limit suggests local thermal adjustment.
abstract: Transformation of earth's ecosystems by anthropogenic climate change is predicted for the 21st century. In many regions, the associated increase in environmental temperatures and reduced precipitation will have direct effects on the physiological performance of terrestrial and aquatic ectotherms and have already threatened fish biodiversity and important fisheries. The threat of elevated environmental temperatures is particularly salient for members of theOncorhynchusgenus living in California, which is the southern limit of their range. Here, we report the first assessments of the aerobic capacity of a Californian population of wildOncorhynchus mykissWalbaum in relationship to water temperature. Our field measurements revealed that wildO. mykissfrom the lower Tuolumne River, California maintained 95% of their peak aerobic scope across an impressive temperature range (17.8-24.6°C). The thermal range for peak performance corresponds to local high river temperatures, but represents an unusually high temperature tolerance compared with conspecifics and congeneric species from northern latitudes. This high thermal tolerance suggests thatO. mykissat the southern limit of their indigenous distribution may be locally adjusted relative to more northern populations. From fisheries management and conservation perspectives, these findings challenge the use of a single thermal criterion to regulate the habitat of theO. mykissspecies along the entirety of its distribution range.
authors.affiliation: Department of Wildlife, Fish and Conservation Biology , University of California Davis , Davis, CA 95616 , USA.
authors.forename: Christine E
authors.initials: CE
authors.lastname: Verhille
authors.affiliation: LGL Limited , Sidney, British Columbia , Canada V8L 3Y8.
authors.forename: Karl K
authors.initials: KK
authors.lastname: English
authors.affiliation: Department of Wildlife, Fish and Conservation Biology , University of California Davis , Davis, CA 95616 , USA.
authors.forename: Dennis E
authors.initials: DE
authors.lastname: Cocherell
authors.affiliation: Department of Zoology and Faculty of Land and Food Systems , University of British Columbia , Vancouver, British Columbia , Canada V6T 1Z4.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Farrell
authors.affiliation: Department of Wildlife, Fish and Conservation Biology , University of California Davis , Davis, CA 95616 , USA.
authors.forename: Nann A
authors.initials: NA
authors.lastname: Fangue
keywords: Oncorhynchus mykiss; aerobic scope; fish; metabolic rate; swimming; temperature