Catch and Effort Data
The objectives of studies on fish population are as follows; firstly, to make a diagnosis of the past and present situation of a stock and give an adequate foundation for optimum yield; secondly, to make a good estimate of the future situation of a sock, and thirdly, to enhance the productivity of a stock if possible. In order to diagnose the present situation of a stock, information on fluctuations in productivity of fisheries is of vital importance. Such information can be obtained from the fisheries statistics data which are mainly compiled by the Statistics Section of the Department of Fisheries of a country. These data consist of two main components, i.e., catch and effort data on populations of commercially important fishes. These data also provide some indications on the mechanism of stock fluctuations.