Stock assessment models and methods

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