Pericardial and vascular pressures and blood flow in the albacore tuna, Thunnus alalunga

Pericardial, ventricular, and dorsal aortic pressures, and blood flow were measured in tabled, anesthetized albacore tuna, Thunnus alalunga (7.8-10.7 kg) captured at sea off Monterey, California (USA) during August 1985. Mean pericardial pressure was -10.0/-2.6 cm H2O (Systolic/Diastolic, [S/D]) and mean pericardial pulse pressure was 7.5. Heart rate averaged 87 beats per minute. Mean ventricular pressure was 97.0/12.9 cm H2O [S/D] and mean dorsal aortic pressure was 64. High ventricular and dorsal aortic pressures of albacore reflect the perfusion requirement of its metabolically active tissues and compensate for the energy losses resulting from blood flow through the gills to arterial heat exchanger to capillaries and again back to the venous heat exchanger. As in elasmobranchs, the remarkably high pericardial pulse pressure, large pericardial volume, and negative pericardial pressure in the albacore suggest that its pericardium is more rigid than that of most teleosts and thus facilitates cardiac filling. Published cardiac output values for most non-tunas, when corrected for body size differences, are less than the mean weight specific cardiac output of albacore (29.4 ml/kg per min, range 12.9-51.9).