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 O2 kg-1 h-1) was similar to that measured for fish acclimated and tested at 19°C (8.80±1.42 mg O2 kg-1 h-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.
Highlights
Temperature is well known to affect the behaviour and physiology of fishes both directly and indirectly, influencing the geographical distribution of a species as well as specific physiological processes, such as metabolic rate and growth (Fry, 1971; Schmidt-Nielsen, 1999; Moyle and Cech, 2002)
When fish were tested at 26°C, mortality was higher; three out of four fish acclimated at 15°C and three out of four fish acclimated at 19°C died during routine metabolic rate (RMR) measurements
No clear peak in absolute aerobic scope (AAS) was observed with test temperatures up to 23°C because the response of AAS of fish acclimated at 15°C to test temperature (Fig. 1C) was fitted with the following non-significant (P = 0.99) relationship: AAS = 7.11 + 0.002x
Summary
Temperature is well known to affect the behaviour and physiology of fishes both directly and indirectly, influencing the geographical distribution of a species as well as specific physiological processes, such as metabolic rate and growth (Fry, 1971; Schmidt-Nielsen, 1999; Moyle and Cech, 2002). Absolute aerobic scope defines the maximal aerobic capacity available at a given temperature to perform the activities essential for survival that extend beyond routine maintenance of life to include ecologically relevant and important functions (i.e. swimming, foraging, growth, etc.; Pörtner and Knust, 2007; Pörtner and Farrell, 2008; Clark et al, 2013). It does not predict when or how these activities are used (Farrell, 2016). The OCLTT hypothesis has emerged as a conceptual model to assess thermal performance of aquatic animals and to determine the fundamental thermal range for a particular species (Pörtner, 2001; Pörtner and Knust, 2007; Pörtner and Farrell, 2008), but not without some debate (e.g. Clark et al, 2013; Farrell, 2013; Pörtner and Giomi, 2013; Norin et al, 2014)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
