Stock assessment models and methods

Fish stocks have an important role in providing cheap protein food, income and employment \nto millions of people in the world. Judicious management and exploitation of the renewable \nfish resources is important for sustained production over years. Over fishing leads to \ndisappearance of the renewable fish stocks. Assessment of fish stocks is the first step to \ndetermine the level of exploitation necessary for arriving at maximum sustainable yields from \nthe fish resources. Assessment of stocks and study of impact of present level of exploitation \non exploited stocks are necessary for maintenance of stocks at maximum sustainable level. \nMany mathematical and statistical models have been developed and used for fish stock \nassessment studies. The unique features of fish stocks are, they do not come under visual \nhorizon for direct evaluation of stock sizes, their distribution over space, time and species \nvaries at higher dimension and fish stocks are affected by fishery dependent factors such as \neffort exerted, size at first capture and fishery independent factors like salinity, temperature, \nwater current etc. The models to study fish stocks should consider the three aspects namely, \nsize of the stock, level of exploitation and effect of fishery independent factors. Multi species \nand multi gear situation adds to the problem of assessing the fish stock. Stock assessment \nmodels satisfying some of these requirements have been developed and successfully used \nfor management of the fishery.