Abstract
The effect of 5, 10, 15 and 20 ppm of zinc sulphate on serum glucose and lactate levels was studied in 9 nutritionally important species of fish from a tropical environment. There was a direct relationship between the depletion of energy reserve and the accumulation of glucose and lactate in serum, which was highest in the major carp (Catla catla, Cirrhima mrigal amd Labeo rohita ), followed by snake-headed (Ophicephalus marulius, O. punctatus and O. striatus ) and cat fish (Mystus seenghala, Clarius batrachus and Heteropneustes fossilis ). The primitive fishes (major carp) appear less resistant than snake-headed or cat fish to face environmental change. The observed physiological and biochemical variations due to zinc intoxication are discussed in relation to mucus formation around the gills, tissue hypoxia, change in the buffering system of tissues and serum, biochemical compartmentalization of fish tissues and the distribution of zinc itself.