Effects of seasonal ambient temperature variations on acute toxicity of chlordane to an air-breathing Indian catfish, Heteropneustes fossilis (Bloch.)

Abstract

Chlordane, widely used in India, is a potential toxicant against soil pests, non-target organisms and humans. FA0 and WHO (1973) have recommended 0.001 mg/kg body weight as the maximum acceptable daily intake (ADI) for chlordane, but no such dose can be recommended safely for fishes. Temperature and pollution are considered as important limiting factors in fisheries and environmental management. The relationship between ambient seasonal temperature and acute toxicity of pesticides in vertebrates is generally believed to be non-linear (Brown 1980). Unlike homeothermic animals, response of the poikilothermic animals to toxicants at varying ambient temperatures is not well understood. While most of the reports in this regard are from the temperate countries, very few studies have been made in the tropics (Rai and Mandal 1990). The present study was undertaken to evolve a regression model for acute toxicity estimates of chlordane at various temperatures to aid fisheries and environmental management. With this in view the relationship of acute toxicity to seasonal variations in temperature has been investigated in a common Indian table fish, Heteropneustes fossilis. MATERIALS AND METHODS Healthy specimens of H. fossilis of length and weight 15.06+ 3.00 cm and 12.20+2.35 g, respectively, were acclimated to the laboratory conditions for 15 d and were fed chopped goat's spleen ad libitum. Feeding was stopped 24 hr prior to treatment. Acute toxicity tests for 48, 96 and 120-hr were conducted employing semidynamic method (Brown 1980) of bath treatment. Water of all the experimental aquaria, including controls was changed every 24 hr. However, water was not changed in the aquaria in which the exposure period was only 24 hr.