Haematological response of Labeo rohita (Hamilton) fingerlings exposed to low salinities

Abstract

The present study was carried out for a period of 42 days to find out the effect of different acclimation salinities (0-control, 2, 4, 6 and 8 ppt) on the haematology of Labeo rohita fingerlings. The fish remained active and showed normal feeding and swimming behaviour up to 4 ppt salinity level; however, at 6 and 8 ppt, they get stressed but were able to survive. There was no significant difference in haematological parameters among fishes in the control, 2 and 4 ppt treatments. Haematocrit (Ht%) values were within the optimum range at 0, 2 and 4 ppt salinity. The mean haematocrit values ranged from 22.21 (at 8 ppt) to 27.03 (control). The highest mean haemoglobin content was observed at 0 ppt (7.09 g dl-1) and it was lowest at 8 ppt salinity (5.36 mg dl-1) on the day of termination of the experiment. Mean total erythrocyte count (TEC) was highest (1.83x106 mm-3) at 2 ppt salinity and the lowest was at 8 ppt salinity (1.52 x106 mm-3). The mean total leukocyte count (TLC) was highest at 8 ppt (4.81x103 mm-3) and the lowest value was recorded at 0 ppt (4.35 x103 mm-3). The mean plasma glucose level at 8 ppt (62.43 mg dl-1) was the highest among the different groups and lowest of 44.70 mg dl-1 was seen in control fishes. Results of the study indicated that increasing salinity up to a certain level is tolerated by L. rohita through osmoregulation, however, extreme salinity stress can lead to alterations in the haematology as well as physiology and further the inability to adapt, leads to metabolic downregulation, thereby affecting growth.