author(s)
M Jithesh and MV Radhakrishnan

abstract
The healthy condition of an aquatic ecosystem depends upon the physico-chemical and biological characteristics, which usually fluctuate with season and degree of pollution. The present investigation was carried out to assess the seasonal variations in bioaccumulation of metals (Cr, Mn, Fe, Cu, Zn and Pb) in selected tissues (Gill, Liver, Kidney and Muscle) of the freshwater fish Trichiurus lepturus collected from Chaliyar River, Kerala state. The results showed variation in accumulation of metals in different seasons. Gills accumulated maximum quantities in monsoon period followed by post monsoon, summer and pre monsoon period respectively. Liver, kidney and muscle accumulated maximum in monsoon and post monsoon periods. The order of accumulation was Fe > Zn >Mn> Cu > Cr >Pb. From this study it is clear that the Chaliyar River is polluted due to the discharge of industrial effluents, sewage run off from the villages as well as gold mining activities in the bank of the river by tribal people. The entry of metals into the river system reflects the pollution by industries which may adversely affect the fish population. Hence, to maintain a healthy biodiversity and abundance of fish, educate locals about the negative impact of pollution with sewage, fertilizers, pesticides and other chemicals.