Paravur- Kappil backwaters, a major estuary in Kerala, was studied from six selected stations covering three seasons. Sea sand filling in Paravur backwater was the most important factor controlling the phytoplankton productivity, growth and succession of major number of species. It was observed that, in Paravur -- Kappil backwater, phytoplankton productivity was the important factor controlling the qualitative and quantitative distribution and abundance of fishes. Moreover, temperature, nutrients (nitrate, nitrite, phosphate, and silicate), dissolved oxygen and monsoon variation influenced the fluctuations of phytoplankton productivity. [ABSTRACT FROM AUTHOR]