Aerobic scope increases throughout an ecologically relevant temperature range in coho salmon

Abstract

Aerobic scope (AS) has been proposed as a functional measurement that can be used to make predictions about the thermal niche of aquatic ectotherms and hence potential fitness outcomes under future warming scenarios. Some salmonid species and populations, for example, have been reported to exhibit different thermal profiles for their AS curves such that AS peaks around the modal river temperature encountered during the upriver spawning migration, suggesting species-and population-level adaptations to river temperature regimes. Interestingly, some other salmonid species and populations have been reported to exhibit AS curves that maintain an upwards trajectory throughout the ecologically relevant temperature range rather than peaking at a modal temperature. To shed further light on this apparent dichotomy, we used adult coho salmon (Oncorhynchus kisutch) to test the prediction that peak AS coincides with populationspecific, historically experienced river temperatures. We assessed AS at 10 and 15°C, which represent a typical river migration temperature and the upper limit of the historically experienced temperature range, respectively. We also examined published data on AS in juvenile coho salmon in relation to new temperature data measured from their freshwater rearing environments. In both cases, AS was either maintained or increased modestly throughout the range of ecologically relevant temperatures. In light of existing evidence and the new data presented here, we suggest that when attempting to understand thermal optima for Pacific salmon and other species across life stages, AS is a useful metric of oxygen transport capacity but other thermally sensitive physiological indices of performance and fitness should be considered in concert.

Short‐Term Physiological Disruption and Reflex Impairment in Shortnose Sturgeon Exposed to Catch‐and‐Release Angling

“…; Raby et al. ). Characteristics of catch‐and‐release angling episodes, such as air exposure, fight duration, and water temperature, can cause unrecoverable physiological disruptions (Cooke et al.…”

Temperature preference, aerobic scope and upper thermal tolerance in sympatric juvenile chinook slamon (Oncorhynchus tshawytscha) and coho salmon (O. kisutch)

“…Several studies in juvenile salmonids have yielded similar results to that of and Raby et al (2016). In juvenile coho salmon from the Seymour River hatchery in BC, Casselman et al (2012) found that aerobic scope was maintained or even continued to increase slightly across ecologically relevant temperature ranges.…”

“…Clark et al (2011) found that aerobic scope in adult pink salmon (O. gorbuscha) continued to increase at temperatures higher than the fish would have experienced at any point in their life cycle, peaking at 21 ºC and only starting to decline at approximately 23 ºC. Another study done by Raby et al (2016) testing aerobic scope in adult coho salmon also found that performance was maintained across ecologically relevant temperatures, those that the fish were likely to encounter at any point in their life cycle.…”

Reply to Zhang & Gilbert (2017): Comment on ‘Measurement and relevance of maximum metabolic rate in fishes by Norin & Clark (2016)’

“…Zhang and Gilbert cite a few studies where this may be the case, but they fail to acknowledge recent literature, including an extensive meta‐analysis, which finds that in most fish species increases over most of the measured temperature range, showing no or only a minor decline as lethal temperatures are approached (Clark et al ., 2013 a , b ; Jutfelt et al ., ; Norin et al ., ; Lefevre, ). Indeed, we encourage Zhang and Gilbert to focus on ecologically‐relevant temperatures when examining these concepts (Clark et al ., ; Raby et al ., ). To counter more of Zhang and Gilbert's concerns, the meta‐analysis also finds little evidence for differences in the shape of the thermal performance curve for both and aerobic scope in acclimated v .…”