THE STANDARD METABOLIC-RATE OF DOLPHIN FISH

The standard metabolic rates (SMRs) of 11 (1.395-4.125 kg) dolphin fis h (mahimahi or dorado, Coryphaena hippurus) were measured at 25 degree s +/- 0.5 degrees C. Fish were prevented from swimming with neuromuscu lar blocking agents and force ventilated. Heart rates were determined simultaneously. SMRs (358-726 mg O-2 h(-1)) were several times those o f other similarly sized active teleosts such as salmonids, but close t o those of tunas. Heart rates (84-161 beats min (-1) ) were also high, but alike those of tunas under similar circumstances. As in tunas, th e high SMR of dolphin fish may result from high osmoregulatory costs e ngendered by their large gill surface areas and/or other adaptations n ecessary for achieving exceptionally high maximum metabolic rates.