Acute Toxicity Assessment of Mercury Chloride to Freshwater Air Breathing Fish Clarias batrachus (Linnaeus, 1758): In vivo Study

Background: Mercury is the most noxious heavy metal. Because of its environmental persistence and ability to be accumulated in the fatty tissues of aquatic organism, it poses serious threat to the fish community.Methods: In the present study, freshwater air breathing fish Clarias batrachus were exposed separately to different concentrations of Mercury chloride (HgCl2) for 24 hrs, 48 hrs, 72 hrs and 96 hrs. Firstly, median lethal concentration (LC50) of HgCl2 to fish was determined by Probit analysis and was confirmed by pilot test. The behavioral and locomotary changes were monitored.Result: Test group showed random irregular and rapid swimming, restless activity. Along with these activities the test group became hyperactive, started jumping and changing their direction and position in an irregular manner. Some of the noticeable physiological symptoms during the initial stage of toxicity assessment were rapid opercular movement and frequent gulping of air. Both jerky movement and rapid respiratory response were reported to be occasional and slower in the longer duration exposure. Acute toxicity assessment provides first hand information to keep a check on pollution and to observe and track rigours of aquatic ecosystems.