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. The present textbook has been prepared to give the SEAFDEC trainees a basic knowledge of fish population and show a brief guideline on haw to evaluted "the current situation of fisheries" and how to treat catch and effort data. It is vased on revisions and summaries of several working papers presented by the author at technical workshops and seminars held at SEAFDEC, Bangkok, in 1979-81. Most of the references cited in this book are from Japanese technical papers mainly related to selected pelagic fish species around Japanese coastal waters