Sex-specific differences in swimming, aerobic metabolism and recovery from exercise in adult coho salmon (Oncorhynchus kisutch) across ecologically relevant temperatures

Abstract

Adult female Pacific salmon can have higher migration mortality rates than males, particularly at warm temperatures. However, the mechanisms underlying this phenomenon remain a mystery. Given the importance of swimming energetics on fitness, we measured critical swim speed, swimming metabolism, cost of transport, aerobic scope (absolute and factorial) and exercise recovery in adult female and male coho salmon (Oncorhynchus kisutch) held for 2 days at 3 environmentally relevant temperatures (9°C, 14°C, 18°C) in fresh water. Critical swimming performance (Ucrit) was equivalent between sexes and maximal at 14°C. Absolute aerobic scope was sex- and temperature-independent, whereas factorial aerobic scope decreased with increasing temperature in both sexes. The full cost of recovery from exhaustive exercise (excess post-exercise oxygen consumption) was higher in males compared to females. Immediately following exhaustive exercise (i.e. 1 h), recovery was impaired at 18°C for both sexes. At an intermediate time scale (i.e. 5 h), recovery in males was compromised at 14°C and 18°C compared to females. Overall, swimming, aerobic metabolism, and recovery energetics do not appear to explain the phenomenon of increased mortality rates in female coho salmon. However, our results suggest that warming temperatures compromise recovery following exhaustive exercise in both male and female salmon, which may delay migration progression and could contribute to en route mortality.

Population variability in thermal performance of pre-spawning adult Chinook salmon

“…Generally, these temperature ranges are consistent with previous findings for migrating adult Chinook salmon thermal limits, which wait at river mouths and slow their migration when river temperatures are too warm (20–23.9°C Columbia River; 19–21°C Sacramento River) ( Fish and Hanavan, 1948 ; Hallock et al, 1970 ; Richter and Kolmes, 2005 ; Goniea et al, 2006 ; Keefer et al, 2018 ; for review see McCullough, 2001 ). We did not find major differences in Topt AAS between the populations and this might be because we did not test fish within the thermal range that is likely to be “optimal” (14–17°C) as measured in sockeye and coho ( O. kisutch ) salmon ( Eliason et al, 2011 ; Kraskura et al, 2021 ) and instead focused on testing fish at the supraoptimal temperatures to define temperatures where performance would collapse.…”

“…We measured short-term recovery with three estimates: (1) Percent of AAS (%AAS), calculated as the MO 2 recovered as a function of the AAS following each exercise calculated at time points 0, 10, 20, 30, 40 and 50 min; (2) percent of MMR (%MMR), calculated as the MO 2 value as a function of the MMR 1h or MMR 18h following the respective exhaustive exercise, calculated at time points 0, 10, 20, 30, 40 and 50 min; and (3) the time to recover to 50% of respective MMR (recMMR 50 ) ( Kraskura et al, 2021 ). Individuals without a distinct measurement between 48 and 52% of MMR were excluded from recMMR 50 analyses.…”

“…To complete upstream migration, salmon need to minimize both the duration and energetic costs of recovery ( Claireaux et al, 2000 ; Suski et al, 2007 ; Eliason and Farrell, 2016 ). However, warming river temperatures may prolong recovery time ( Prystay et al, 2017 ; Kraskura et al, 2021 ), which has clear fitness costs and could result in migration failure in Pacific salmon ( Jain and Farrell, 2003 ; Lee et al, 2003a ; Eliason et al, 2011 ; Burnett et al, 2014b ; Raby et al, 2015 ).…”

Habitat fragmentation drives divergent survival strategies of a cold‐water fish in a warm landscape

“…We also estimated the recovery time fish would need to resume these activities after exhaustion. We used the time elapsed before MO 2 fell below 50% of MMR, a level at which other salmonids are able to fully recover their swimming ability (Eliason et al, 2013; Kraskura et al, 2021). Background respiration was negligible for both experiments, and the data were not adjusted to account for background respiration (Appendix S1).…”

Despite plasticity, heatwaves are costly for a coral reef fish

“…At the same time, other vital processes may become more energetically costly at high temperatures, such as digestion (specific dynamic action, SDA) 16 and recovery from exertion 17 . Thus, during marine heatwaves, fish may be less able to perform certain activities (i.e., swimming, eating, reproduction, or territoriality) within their constrained energy budget 18 , 19 .…”