Effects of daily management stress on haematology and blood rheology of the gilthead seabream

Haematological and haemorheological responses against a moderate management stress, applied for 2 weeks, have been studied in the gilthead seabream (Sparus aurata). The stress application leads to a significant reduction in circulating erythrocytes, which caused decreased blood viscosity. Although erythrocyte osmotic fragility showed a trend inversely related to the duration of management stress, no significant change in cell dimensions, aggregation and deformation indices was observed. Consequently, the decrease in oxygen transport capacity attributable to haematocrit reduction, is not compensated by a qualitative change in the microrheological behaviour of erythrocytes, since the blood viscosity decreases as a direct result of the decline in red blood cell number. © 1995 The Fisheries Society of the British Isles.