Comparatively little attention has been paid to hydrobiological investigations on the inland waters in India . Kerala State is noted for its possession of a net work of streams, scattered ponds and lakes . Many of these are yet to be investigated and hence it was thought that a survey of the hydrobiological aspects of some of these would yield useful data. This is a preliminary report on the survey of Beypore river of Calicut district in Kerala State for the year 1964 . It has its origin in the Nilgiri Hills and empties into the Arabian Sea (Fig . 1) .
Feroke and Mavur were selected as two stations for the study, Feroke being 3 .6 km above the outfall is in the tidal zone, whereas Mavur is 28 .5 km above the outfall and forms the upper limit of the tidal zone . At Mavur, the river has a width of 0 .3 km and at Feroke it is of approximately the same width . This river never dries up and during monsoons, the water level rises by 10' to 12' at Feroke and 30' at Mavur . The bottom deposits of this river at both the stations consist essentially of fine sand . Mavur station is located further above the Rayon Pulp Factory at Mavur (Fig . 1) . Hydrobiological conditions of the polluted region near the dumping spot of effluents from the Factory will be dealt with in detail elsewhere . Monthly observations were made on water samples collected for temperature, pH, dissolved oxygen content and salinity. Quantitative measurements of plankton collected in a standard plankton net were done by counting them in a counting chamber . Dissolved oxygen content was determined by