 Ram ventilation is said to be obligatory in southern bluefin tunas, because the buccal-opercular pump system used by other teleost fish became incapable of producing a stream of ventilation vigorous enough for their needs.All species of tuna in general have lost the opercular pump, requiring a quicker movement of oxygenated water over the gills than induced by the suction of the opercular pump.Therefore, if they stop swimming, tunas suffocate due to a lack of water flow over the gills.