The fish production from marine sector is contributed by the wild capture that is happening from the sea. There are nearly 1 million active fishermen and nearly 4 million people directly or indirectly involved in this fishing activity. They harvest nearly 3.5 million tonnes of fish every year. Scientific studies have estimated Indian marine fisheries potential as 4.41 million tonnes. This indicates that our resources are exploited almost to its potential level and we have very few untapped resources. The fish production in the sector is contributed by more than 800 species of fish that constitute our commercial fishery. Most these species are not exploited in a sustainable manner. In India, the capacity of fishing fleets is more than our harvestable potential. Therefore it is imperative to know the stock size of various commercially harvested species. It is difficult to really estimate the fish biomass in the sea. It is like lifting the entire fish biomass form the seas and estimating the mass of individual species also and arriving at a potentially harvestable value. With various concentrated efforts in fisheries science, CMFRI was able to deduce few mechanisms to estimate the fish stock available in our coastal waters. Since long officials from CMFRI have been involved in gathering the species-wise and gear-wise information on fish landings from around 1300 landing centres based on a scientifically designed estimation procedure known as stratified multi stage random sampling method. The estimates of landings along with the fishing effort expended and the data on the biology of various species collected enable us to identify whether a stock is over exploited. Few years back CMFRI developed a rapid stock assessment method too. Based on such assessment methods, the information on stock status of various species was ascertained and the knowledge is passed on to policy planners at international, national and state/UT level for management of fishery