Haematology and leucocyte morphology of wild caught Thunnus maccoyii

The haematology of wild southern bluefin tuna Thunnus maccoyii was described using blood samples collected from fish immediately after they were caught. Cytology and cytochemistry revealed that the blood in peripheral circulation is comprised of erythrocytes, reticulocytes, ghost cells, lymphocytes, thrombocytes, eosinophilic granulocytes, neutrophilic granulocytes and monocytes. Reference ranges established were 41.09-55.50% for haematocrit, 0.62-3.00% for leucocrit, 13.25-17.92 g dl-1 for haemoglobin and 2.1-2.9 million erythrocytes μl-1 for erythrocyte count. Differential cell counts showed 94.58 ± 2.15% erythrocytes, 3.99 ± 1.44% leucocytes and 1.43 ± 1.03% thrombocytes (mean ± S.D.). Normal ranges for differential leucocyte counts were 0.00-5.45% for neutrophils, 0.69-12.06% for eosinophils, 0.00-5.03% for monocytes, 46.97-74.32% for lymphocytes and 14.47-43.92% for thrombocytes. Erythrocyte indices, leucocyte types and cytochemistry were comparable to other species of scombrids. Packed cell volume was sensitive to the physiological state of the fish and to sample handling technique. © 2005 The Fisheries Society of the British Isles.