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Characteristics of Acoustic Scattering according to Pulsation of the Large Jellyfish Nemopilema nomurai

노무라입깃해파리의 박동에 따른 음향산란 특성

  • Yoon, Eun-A (Faculty of Marine Technology, Chonnam National University) ;
  • Hwang, Doo-Jin (Faculty of Marine Technology, Chonnam National University) ;
  • Hirose, Miyuki (Faculty of Marine Technology, Chonnam National University) ;
  • Kim, Eun-Ho (Graduate School of Fisheries Sciences, Hokkaido University) ;
  • Mukal, Tohru (Faculty of Fisheries Sciences, Hokkaido University) ;
  • Park, Byung-Soo (Dept. of Maritime Police & Production System, Gyeongsang National University)
  • Received : 2010.07.26
  • Accepted : 2010.10.04
  • Published : 2010.10.31

Abstract

The large jellyfish Nemopilema nomurai causes serious damage to fisheries, particularly around the seas of Korea and Japan. Decreasing this damage requires knowledge of the distribution and abundance of jellyfish. Acoustic technology using quantitative echosounders is one method of studying the distribution and abundance of jellyfish. Such methods are commonly used worldwide because they have the advantage of providing substantial information about all water layers in a wide area in a short time. However, in order to conduct an acoustic survey, the acoustic characteristics of the target organism must be known. These can be altered by a number of factors, including pulsation, swimming angle, frequency and size. Accordingly, this study determined the variation in target strength according to pulsation of N. nomurai. Data were analyzed for two jellyfish with bell diameters in air of (a) was 32.0 and (b) 25.0 cm. The pulsation cycle of jellyfish (a) was 1.5~2.0 sec and the target strength (TS) cycle was 1.0~2.5 sec, while jellyfish (b) had a pulsation cycle of 1.0~1.5 sec and TS cycle of 1.0~3.0 sec. The variation width of the TS with the change in pulsation was 7.8 dB (-72.4~-64.6 dB) for jellyfish (a) and 10.3 dB (-71.6~-61.3 dB) for jellyfish (b). The variation in bell diameter was about 0.28 and 0.35, respectively. These results confirmed that the variation in bell diameter caused by pulsation is closely related to the variation in TS.

Keywords

Acknowledgement

Grant : 한일주변해역에 있어서의 동물플랑크톤의 음향산란층의 규명

Supported by : 한국연구재단

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