Author(s): M. DASGUPTA

Abstract: The present communication is on the adaptation of the alimentary canal to feeding habit of the weed eating fish Ctenopharyngodon idella (Val.) from Nadia District of West Bengal. The morphology of the alimentary canal, relative dimensions of different parts of the alimentary canal in the total length of the alimentary canal (morphometrics); relative length of the gut (R.L.G.) at different groups of the fish have been studied in relation to the food and feeding habit of the fish. The gut content analysis of the fish has been done at different length groups of the fish. The pattern of mucosal folds at the different regions of the alimentary canal of the fish has been described. Morphology of the alimentary canal and relative dimensions of different parts of the alimentary canal suggests its herbivorous feeding habit. The fish has been found to depend on food of animal origin at its early stages. In the juvenile stage the fish preferred food of both plant and animal origin . In the advanced stages the fish depended only on aquatic macrophytes. The R.L.G. value varied from 0.8 to 2.5. the value increased with the increase of vegetable matter in the gut content. The R.L.G. value of the adults (2.5) suggests that the gut is rather short when compared to other herbivours. The pattern of mucosal folds at different regions of the alimentary canal was found to vary for performing different functional roles. The fish has been recommended for control of aquatic weeds. Their feeding strategy could be altered by providing them with cheaper food from indigenously available raw materials of plant origin to make fishery operation more economic..

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