The presence of x-cell disease in Antarctic fish, a disease that affects the gills by producing lesions on the gill tissue, has been shown to affect the ability of the fish to take up oxygen and can cause problems with blood flow through the gills. The effect of x-cell disease on aspects of cardiovascular and respiratory physiology was investigated in resting and exercised fish and in healthy and ... diseased fish. Fish had cannulae inserted in the afferent branchial artery to measure ventral aortic (pre gill) blood pressure and heart rate and in the efferent branchial artery (post gill) to measure dorsal aortic blood pressure. Blood flow through the ventral aorta, PO2 and the oxygen content in the blood of x-cell infected fish was also measured. The heart of diseased fish was examined to elucidate whether the chronic hypertension has any effect. The stress physiology of fish was also investigated with measurements of blood pressures and heart rates from the ventral and dorsal aortae in fish that were stressed. Blood samples were collected for measurements of catecholamines, osmolarity, haematocrit and glucose, all indicators of stress.