  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{\deg}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{\deg}C-acclimated fish. 20{\deg}C-acclimated mahi experienced significantly
decreased aerobic scope and Ucrit relative to 28{\deg}C-acclimated fish (57 and
28% declines, respectively). 32{\deg}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{\deg}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{\deg}C), aligns with recently observed habitat utilization patterns for
wild mahi and could be relevant for climate change predictions.
