A general swimming response in exhausted obligate swimming fish

Marine organisms normally swim at elevated speeds relative to cruising
speeds only during strenuous activity, such as predation or escape. We
measured swimming speeds of 29 ram ventilating sharks from 10 species and
of three Atlantic bluefin tunas immediately after exhaustive exercise
(fighting a capture by hook-and-line), and unexpectedly found all
individuals exhibited a uniform mechanical response, with swimming speed
initially 2 times higher than the cruising speeds reached approximately 6
hours later. We hypothesised that elevated swimming behaviour is a means
to increase energetic demand and drive the removal of lactate accumulated
during capture via oxidation. To explore this hypothesis, we estimated the
mechanical work that must have been spent by an animal to elevate its swim
speed, and then showed that the amount of lactate that could have been
oxidized to fuel it comprises a significant portion of the amount of
lactate normally observed in fishes after exhaustive exercise. An estimate
for the full energetic cost of the catch-and-release event ensued.