Fishery Technology 2008, Vol. 45(2) pp : 209 - 216 Seasonal Variation in Biochemical Composition of Edible Oyster (Saccostrea cucullata) from Indian Sundarbans Abhijit Mitra*, Shibdas Basu* and Kakoli Banerjee" * Department of Marine Science, University of Calcutta, 35, B.C. Road, Kolkata 700 019. " WWF-India Secretariat, Tiger and Wildlife Programme, Canning Field Office, 24 Parganas (South), West Bengal - 743 329. Protein, lipid, glycogen, moisture and ash content of the edible oyster species were analysed on monthly basis during 2004 and 2005 from the cultured site at Chotomollakhali in eastern sector of Indian Sundarbans. The culture of edible oyster was initiated in this part of the country in order to provide alternative livelihood to the poverty stricken population in the Indian Sundarbans, which may otherwise, lead to destruction of natural resources of this mangrove ecosystem. Simultaneous monitoring of hydrological parameters (surface water temperature, salinity, pH, nitrate, phosphate and silicate) and phytopigment level of the ambient water was also carried out in this cultured site to investigate the interrelationship between the hydrological parameters and biochemical composition of the oyster tissue. The two year study indicates significant seasonal oscillation of the major biochemical constituents of the oyster. Key words: Indian Sundarbans, mangrove, phytopigment, Saccostrea cucullata. Indian Sundarbans is one of the most biologically productive and taxonomically diversified, low-lying, mangrove detritus based, open, dynamic, heterogeneous coastal ecotone situated at the apex of the Bay of Bengal (between 210132 to 22o402 N la titude and 88o032 to 89o072 E longitude). The entire forest of this unique ecosystem acts as a potential reservoir of marine bio tic resources. The lower stretch of the estuarine complex and high saline zones are extremely favourable for the survival and growth of edible oyster (Mitra & Banerjee, 2005). Saccostrea cucullata is the dominant oyster species in Indian Sundarbans although Crassostrea gryphoides and Crassostrea madrasensis are also reported in the basal part of hard substrata (like sluice gates, jetties, pillars of fish landing stations, light house etc.). Oyster is a good source of protein, vitamins, minerals and trace ele- ments. Researchers have collected detailed information on biochemical composition of edible oysters, largely because they can be valuable food (Tack et al, 1992; Ruwa & Polk, 1994). However, many internal and environ- mental factors including pollutants can affect the growth and reproductive success of marine bivalves and can also affect biochemi- cal composition. (Mac Donald & Thompson, 1985; Steelk & Mulcahy, 1999). The present investiga tion highlights the seasonal varia- tion of biochemical composition (% lipid, % protein, % glycogen, % moisture and % ash) in the edible oyster (Saccostrea cucullata) sampled from the eastern sector of Indian Sundarbans with respect to hydrobiological parameters. Materials and Methods The entire network of the present programme comprised of the monthly sam- pling and collection of oysters (Saccostrea cucullata) from Chotomollakhali island in the eastern sectors of Indian Sundarbans for a period of two years (2004-2005) along with