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Summary report on cruise of the R/V Shoyo Maru in the north Arabian Sea, 2 October 1976 - 13 January 1977

Year of publication 1977

Pages 83

Author Yamanaka, H.;Yukinawa, M.;Nakamura, I.

Publisher FAO ;

Product type Document

Edition 1

Synopsis (short abstract) At the Fifth session of the IOFC Executive Committee held in Rome in April 1976, the Indian Ocean Programme reported its success in bringing the R/V Shoyo Maru to the Arabian Sea and adjacent waters off India and Pakistan in November and December 1976. The present paper gives a brief description of the survey and its results, summarized from the original report in Japanese which will be published by the Fishery Agency of Japan in 1977. The activities covered oceanographic observation, convention al biological survey (sighting of pelagic shoals and collection of fishes) and acoustic survey. In spite of special attention, the squid Sympleototeuthis oualaniensis did not appear abundantly during the present cruise. The equatorial undercurrent did not exist in the equatorial waters during the transitional period, from the southwest monsoon to the northeast monsoon. Although the upwelling was recognized in the western part of the Second Area in the 1975 cruise, this was not encountered in the 1976 cruise. This might be attributed to the difference in the survey period; the first cruise in 1975 covered the late southwest monsoon season while the present cruise the early northeast monsoon season. The coastal upwelling on the continental slope was evidently less remarkable during the present cruise than during the previous one. The pelagic shoals again appeared rather scarce in the offshore waters throughout the survey period as was the previous cruise. There was a considerable number of important commercial fishes, almost the same species of the previous survey, on the Pakistani continental shelf, but none of them appeared to be large enough to attract a large-scale operation. In the present survey, the squids were not caught as often as in the previous survey. The index of echo abundance in the Second Area in 1976 was half of that in 1975. Since the duration of our cruise was very limited, it was difficult to find any reasoning for such year-to-year variation. However, it might be suggested that the squids moved toward the west coast of India or the southern Arabian Peninsula, or a deeper layer during the northeast monsoon season.

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    Summary report on cruise of the R/V Shoyo Maru in the North Arabian Sea, 2 October 1975 - 14 January 1976 1976
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    As reported in the Fourth Session of the IOFC Executive Committee held in Rome in October 1974, the efforts of IOP in bringing the R/V Shoyo Maru to participate in the North Arabian Sea survey succeeded when the vessel undertook cruises along the waters of Pakistan in November/December 1975. The present paper gives a brief description of the survey and its results, summarized from the original report in Japanese which has been published by the Fishery Agency of Japan in July 1976. The activities covered oceanographic observation, conventional biological survey (sighting of pelagic shoals and collection of fishes) and acoustic survey. A rendez-vous with the R/V Dr. F. Nansen, the main vessel for the North Arabian Sea survey, for calibration of acoustic instruments was a special feature of the survey. The up-welling supposedly to be remnant of the southwest monsoon phenomenon was located at 23°N, 63°E as late as November during the year of survey. Another up-welling noticed in the vicini ty of 24°N, 66°E was interpreted as one inherent to the continental slope. The pelagic shoals appeared rather scarce in the offshore waters covered by the vessel and the demersal fishes were located mainly in the continental slope. The demersal catch included longspine seabream, giant catfish, Jarboua therapon, threadfin breams, brushtooth lizardfish and sweetlips. Indications of substantial stock of squids were noticed in the offshore waters around the up-welling area. The squids appear to sink to deeper layers of 100-350 mt during daytime and move to the upper layer at night and are easily hooked by jigs.
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    In the plans for resource assessment surveys of the Indian Ocean Fishery Survey and Development Programme, the highest priority has been given to a survey of the pelagic resources off the North Arabian Sea. The main aim of this survey, based primarily on acoustic observations of fish, is to provide information on the identity and size of the major stocks and their exploitable level, the main patterns of distribution and their general life history and behaviour. Even though problems of target ide ntification still exist, the usefulness of acoustic methods has been demonstrated in a number of applications. This plan describes the instruments and tools to be used for the survey and also discusses the principles of the methods to be employed. The efficiency of a survey is limited by weather and ship size. A ship of not less than 150ft in length is recommended and it is assumed that the survey based on echo-sounding and trawling can be carried out through the whole year with the exception of the month of July, when the monsoon is at its peak. Because of the poor knowledge of fish distribution and behaviour in the Arabian Sea the survey coverage should be as frequent as possible and should extend over one year in order to compensate for annual variations in abundance and distribution of stocks. To provide adequate coverage, two vessels will be required for two years on the basis of 200 to 220 days of work per year. Close coordination with other surveys and investigations in the area should be established and the investigatory methods standardized. While the study of the physical and chemical processes of the Arabian Sea are not given high priority, such processes will be observed as part of the study of the nexus between distribution and behaviour of fish and environmental factors, as well as for their general oceanographic value. All data and observations will be logged on special forms, processed on a seasonal and area basis and evaluated. Quarterly reports will be submi tted and a status report prepared after one year of operation.
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