Effect of stocking density and journey length on the welfare of rohu (<Emphasis Type="Italic">Labeo rohita</Emphasis> Hamilton) fry

The effect of higher packing density and increased duration of transport on the survival and key metabolic enzymes of Labeo rohita fry was investigated. L. rohita fry (length 40 ± 5 mm, weight 0.60 ± 0.13 g) were packed in two different densities 40 and 80 g/l and sampled at 0, 12, 24, and 36 h after packing. Results showed that packing density and length of confinement severely affected the survival of the fry. The whole-body glucose level and the activities of the enzymes, lactate dehydrogenase (LDH), malate dehydrogenase (MDH), glucose-6-phosphatase (G6Pase), fructose-1, 6-bisphosphatase (FBPase), aspartate amino transferase (AST), alanine amino transferase (ALT), and adenosine triphosphatase (ATPase) assayed from the fish whole-body significantly (P < 0.05) increased due to increase in the length of the confinement. However, acetylcholine esterase (AchE) activity decreased significantly (P < 0.05) with increase in the length of confinement. Similarly, higher packing density also significantly (P < 0.05) increased the glucose level and activities of all these enzymes (except AchE). The results revealed that both higher packing density and increased transportation duration mobilize protein resources for glucose production via gluconeogenesis and subsequently activate the glycolysis pathway for energy. The rise in the ATPase activity indicates disruption of the osmoregulatory function and the role of this enzyme in ameliorating it. Overall results suggest that normally practiced packing density of 40 g/l is optimum up to 24-h duration for seed transportation.     

Biochemical and histological changes in the brain tissue of spotted murrel, <Emphasis Type="Italic">Channa punctatus</Emphasis> (Bloch), exposed to endosulfan

The present experiment was conducted to establish the relationship between selected physiological parameters and histological responses of Channa punctatus brain tissue to endosulfan exposure. The fish (35.6 ± 0.7 g) was exposed to sublethal endosulfan concentration (8.1 μg l⁻¹) for a period of 12, 24, 36, 48, 72, and 96 h. Results showed that brain glucose level increased significantly after exposure, indicating a hyperglycemic state of the fish. Brain vitamin C level decreased with an increase in the exposure time. Acetylcholine esterase and adenosine triphosphatase enzyme activities also showed a significant reduction upon endosulfan exposure. Brain histopathology after 96 h endosulfan exposure showed that the apical lobe of the cerebrum (the only portion examined) had mild necrosis. Focal area of gliosis could be seen in the cerebrum, which were absent in the control fish. The results indicate that exposure of sublethal concentration of endosulfan to C. punctatus may have a direct effect on the histology of the fish's brain tissue, thereby affecting its metabolism.