Studies on the Behaviour of Fish Schools in the Main-Net of a Large Scale Set-Net Using a Scanning Sonar ( III ) - The Behaviour of Anchovy Engraulis Japonica Sonar-III

소나 관찰에 의한 대형정치망내 어군행동의 연구 ( III ) - 원통내 멸치어군의 행동과 원통의 기능

  • Published : 1996.09.01

Abstract

The moving behaviour of anchovy schools(There were small schools of sardine and round-herring in this anchovy schools} in the bag - net of a large scale set - net was investigated using a scanning sonar, in the Kishihata set - net fishing ground located in Nanao city Ishigawa prefecture, Japan from Dec. 1st to Dec. 4th, 1992. The results obtained are summarized as follows ; 1. Moving behaviour of fish schools between two bag - nets was more in the daytime than in the nighttime. 2. The rate of entering fish schools from the first bag -- net to the second bag - net were 78% when the fish school in the second bag -- net existed. The result suggest that fish school existence in the second bag - net affected the rate of entering fish schools from the first bag - net to the second- bag - net. However, the time of stay of fish school that entered the second bag -- net was very short when the fish school in the second bag - net existed densely. The result suggest that a high fish density in the second bag - net might enlarge the escape rate 3. The majority of fish schools moved to the center and off shore side of the bag - net when fish schools entered the bag - net.

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