Adult female Pacific salmon can have highermigrationmortality rates thanmales, 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^oC, 14^oC, 18^oC) in fresh water. Critical swimming performance (U_crit) was equivalent between sexes and maximal at 14^oC. 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^oC for both sexes. At an intermediate time scale (i.e. 5 h), recovery in males was compromised at 14^oC and 18^oC 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.

All methods are described in the original published article and its supplemental material. 

Data attached contains an excel file with 3 sheets: 1) metadata, that defines the columns and describes the units and metrics themselves, 2) intermittent flow respiromtery data, blood biochemistry parameters, and body morphometrics, 3) swim performance data, fish morphometrics. Any missing values are indicated as NA and were not reported due to technical or experimental limitations (e.g, equipment failure).