Abstract
Mahi-mahi (Coryphaena hippurus) are a highly migratory pelagic fish, but little is known about what environmental factors drive their broad distribution. This study examined how temperature influences aerobic scope and swimming performance in mahi. Mahi were acclimated to four temperatures spanning their natural range (20, 24, 28, and 32°C; 5–27 days) and critical swimming speed (Ucrit), metabolic rates, aerobic scope, and optimal swim speed were measured. Aerobic scope and Ucrit were highest in 28°C-acclimated fish. 20°C-acclimated mahi experienced significantly decreased aerobic scope and Ucrit relative to 28°C-acclimated fish (57 and 28% declines, respectively). 32°C-acclimated mahi experienced increased mortality and a significant 23% decline in Ucrit, and a trend for a 26% decline in factorial aerobic scope relative to 28°C-acclimated fish. Absolute aerobic scope showed a similar pattern to factorial aerobic scope. Our results are generally in agreement with previously observed distribution patterns for wild fish. Although thermal performance can vary across life stages, the highest tested swim performance and aerobic scope found in the present study (28°C), aligns with recently observed habitat utilization patterns for wild mahi and could be relevant for climate change predictions.
Highlights
Temperature is a vital factor dictating swimming performance and aerobic capacity in fish (Clark et al, 2013)
Our results demonstrated that mahi performance was highest around 28◦C, where we observed the largest aerobic scope and Ucrit (Figures 1,2)
Fish in the present study were tested at an earlier age than wild-tagged adults, our results tended to align with thermal ranges reported from pop-up satellite archival tags (PSATs) data obtained from adult wild mahi (Schlenker et al, 2021)
Summary
Temperature is a vital factor dictating swimming performance and aerobic capacity in fish (Clark et al, 2013). Since all life stages are typically and most often found in surface waters, and at the same geographical distribution, we cautiously compare findings from this study to recent patterns noted in wild larger adult mahi fitted with PSATs (Schlenker et al, 2021) that are logistically difficult to obtain and test using swim tunnel respirometry. In addition to these lab-based measurements potentially providing insight into habitat utilization patterns, this study could help us understand how mahi may respond to global projected temperature increases for the present century of 1– 4◦C (Masson-Delmotte et al, 2018). Given current knowledge from catch rates and PSATs, we hypothesized that mahi acclimated to the lowest (20◦C) and the highest (32◦C) temperatures would show declines in aerobic scope and swimming performance
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