title: Unusual aerobic performance at high temperatures in juvenile Chinook salmon,Oncorhynchus tshawytscha.
abstract: Understanding how the current warming trends affect fish populations is crucial for effective conservation and management. To help define suitable thermal habitat for juvenile Chinook salmon, the thermal performance of juvenile Chinook salmon acclimated to either 15 or 19°C was tested across a range of environmentally relevant acute temperature changes (from 12 to 26°C). Swim tunnel respirometers were used to measure routine oxygen uptake as a measure of routine metabolic rate (RMR) and oxygen uptake when swimming maximally as a measure of maximal metabolic rate (MMR) at each test temperature. We estimated absolute aerobic scope (AAS = MMR - RMR), the capacity to supply oxygen beyond routine needs, as well as factorial aerobic scope (FAS = MMR/RMR). All fish swam at a test temperature of 23°C regardless of acclimation temperature, but some mortality occurred at 25°C during MMR measurements. Overall, RMR and MMR increased with acute warming, but aerobic capacity was unaffected by test temperatures up to 23°C in both acclimation groups. The mean AAS for fish acclimated and tested at 15°C (7.06 ± 1.76 mg O2kg-1h-1) was similar to that measured for fish acclimated and tested at 19°C (8.80 ± 1.42 mg O2kg-1h-1). Over the entire acute test temperature range, while MMR and AAS were similar for the two acclimation groups, RMR was significantly lower and FAS consequently higher at the lower test temperatures for the fish acclimated at 19°C. Thus, this stock of juvenile Chinook salmon shows an impressive aerobic capacity when acutely warmed to temperatures close to their upper thermal tolerance limit, regardless of the acclimation temperature. These results are compared with those for other salmonids, and the implications of our findings for informing management actions are discussed.
authors.affiliation: Department of Wildlife, Fish and Conservation Biology , University of California , Davis, CA 95616 , USA.
authors.forename: Jamilynn B
authors.initials: JB
authors.lastname: Poletto
authors.affiliation: Department of Wildlife, Fish and Conservation Biology , University of California , Davis, CA 95616 , USA.
authors.forename: Dennis E
authors.initials: DE
authors.lastname: Cocherell
authors.affiliation: Department of Wildlife, Fish and Conservation Biology , University of California , Davis, CA 95616 , USA.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Baird
authors.affiliation: Department of Wildlife, Fish and Conservation Biology , University of California , Davis, CA 95616 , USA.
authors.forename: Trinh X
authors.initials: TX
authors.lastname: Nguyen
authors.affiliation: United States Environmental Protection Agency , Region 9, 75 Hawthorne Street, San Francisco, CA 94105, USA.
authors.forename: Valentina
authors.initials: V
authors.lastname: Cabrera-Stagno
authors.affiliation: Department of Zoology and Faculty of Land and Food Systems , University of British Columbia , Vancouver, BC , 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, CA 95616 , USA.
authors.forename: Nann A
authors.initials: NA
authors.lastname: Fangue
keywords: Conservation; fish; metabolic rate; metabolism; physiology; plasticity