||I. L. Kalikhman, K. I. Yudanov
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Commercial reconnaissance of fish and other aqualic ilems is achieved by various methods and means. One of the main technical means of search and reconnaissance is acoustic location. Acoustic fish location has recently been widely applied to fisheries. It enables efficient investigation of wide expanses of water, location of fish concentrations, determination of their density and depth, estimation of the commercial significance, and a targeted catch. Acoustic technique has proved to be indispensable to fish reconnaissance and fisheries. Mass application of acoustic equipment on search and commercial vessels has made it possible to increase the efficiency of fishing and targeted trawling of concentrations by commercial fleets, thereby enhancing the industrial exploitation of the World Ocean resources. The modern development of fish location is characterized by the aspiration to a wider practical application of the acoustic method of biomass estimation. This has been motivated by slock reduction of some basic species and by the introduction of 200-mile fishery zones on continental shelves. In the near future, wide-scale inculcation of the acoustic method of biomass estimation should lead to an updated system of observation and control in fisheries, which, in turn, will promote greater efficiency in the exploitation of marine resources. For scientific search and fishing purposes, there are many acoustic instruments that allow fish detecting at practically any depth. There are instruments for estimating the density of concentrations, their size composition, and their movement direction and speed. The application of locating equipment under various conditions contributes a great deal to both theoretical and practical investigations. All this enabled developing and deepening the theory of fish location, improving the fish-finding technique as well as the methods of its use. A myriad of publications deal separately with the theoretical, technical, and practical aspects of fish location. The various applications of acoustic instruments in fisheries are presented; questions of species, size, and quantitative interpretation of readings arc considered. The results of these studies arc given, in particular, in the proceedings of the International Symposia and Conferences on Fisheries Acoustics and in a great number of separate papers. Specific aspects of the overall problem of acoustic fish reconnaissance are considered in the books. However, until now. there has not been any work that presents the subject systematically, detailing all major aspects of applying acoustic equipment in commercial fish reconnaissance and offering sufficient analysis of the possibilities of fish-finding technique...