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魚群探知機に現われた記録の解析―5 : 黄海下りえび漁場について(1)


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Title: 魚群探知機に現われた記録の解析―5 : 黄海下りえび漁場について(1)
Other Titles: Analysis of Fish-Finder Records―V.On Winter Shrimp Trawl in the Yellow Sea (1)
Authors: 柴田, 恵司
Authors (alternative): Shibata, Keishi
Issue Date: Sep-1964
Publisher: 長崎大学水産学部
Citation: 長崎大学水産学部研究報告, v.17, pp.25-43; 1964
Abstract: Now fish-finders have been installed to almost all trawlers by fishermen to detect fish, and above all, in the midwater or off bottom trawlings, fishermen have to decide their net hauling depth according to the fish density traced on echograms. Therefore, they have been investigating earnestly to interpret the echotrace. Much has been written about the reverberation of ultrasonic sound at the Yellow Sea and the East Sea by TSUJITA, NISHIMURA, HAMURO and others. The author, on board the two boat trawler, the Tôkaimaru, #33 (belonging to the Taiyô Gyogyô Co.) during the period from 25th Dec., 1963 to 5th Jan., 1964, made a preliminary research on trawling of shrimp (Kôraiebi, Penaeus orientalis, commercial named Taishôebi), from the standpoint of the user of a fishfinder. The details of catch per haul of trawl and plankton nets were shown in Table 1. In this research, the author observed as follows. 1. The reflection loss of Kôraiebi ♀×5, full length 22-24cm, (see Fig. 2) was 38db. 2. The scattering layers (SL)showed remarkable journal migration, but lower SL near the sea bed showed little migration. 3. After his 17 hauls of 7.5cm plankton nets, the author did not prove organisms of SL and supposed that the origin of SL was not only plankton (Schizopoda, Copepoda, Amphipoda, Sagitta and etc.) and marine snow as shown in Fig. 12, but also distinct zone of temperature and salinity of the sea water and exceptionally SL near the sea bed might be by muddy water disturbed by trawl nets. 4. On the 50KC echogram, the number of single traced at the coverage depth of trawl net was also in substantial agreement with the number of fish caught per haul at the rate of water volume covered by trawl net and echo beam, but on the 200KC echogram, it was very difficult to estimate such a relation, as it catches too sensitively, the reverberation from any scatters in the sea water. The author hopes to have a further opportunity of studying above questions.
URI: http://hdl.handle.net/10069/31575
ISSN: 05471427
Type: Departmental Bulletin Paper
Text Version: publisher
Appears in Collections:第17号

Citable URI : http://hdl.handle.net/10069/31575

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