Oxygen binding by the blood and hematological effects of capture stress in two big game-fish: mako shark and striped marlin.

Blood from capture-stressed striped marlin cannot be fully saturated with oxygen in the presence of lactic acid because of a substantial Root effect. Titration of blood to pH 7.6 at 25 degrees C gave an O2 affinity constant, P50 = 17 mmHg. The P50 was highly sensitive to pH showing a Bohr factor phi = delta log P50/delta pH = -0.74. Blood from capture-stressed mako sharks did not show either a Root effect or a significant Bohr effect (delta log P50/delta pH = +0.16). The O2-affinity constant, P50, was 10.6 mmHg at pH 7.6 and 25 degrees C. Hematological measurements following capture gave hematocrit values of 24.2 +/- 8.1% and 32.3 +/- 10.8% for marlin and mako respectively, and high concentrations of blood lactate in both species (15-16 mmol l-1). The O2 transport properties of the blood are discussed in relation to oxygen demand and capture stress.