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Swimming angle and target strength of larval Japanese anchovy (Engraulis japonicus)

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Title: Swimming angle and target strength of larval Japanese anchovy (Engraulis japonicus)
Other Titles: カタクチイワシ(Engraulis Japonicus)シラスの遊泳姿勢とターゲットストレングス
Authors: Ito, Yusuke1 Browse this author
Yasuma, Hiroki2 Browse this author
Masuda, Reiji3 Browse this author
Minami, Kenji4 Browse this author
Matsukura, Ryuichi5 Browse this author
Morioka, Saho6 Browse this author
Miyashita, Kazushi7 Browse this author →KAKEN DB
Authors(alt): 伊藤, 祐介1
安間, 洋樹2
益田, 玲爾3
南, 憲吏4
松倉, 隆一5
守岡, 佐保6
宮下, 和士7
Keywords: Larval Japanese anchovy
Swimming angle
Target strength
Issue Date: Mar-2011
Publisher: Springer Japan
Journal Title: Fisheries Science
Volume: 77
Issue: 2
Start Page: 161
End Page: 167
Publisher DOI: 10.1007/s12562-011-0323-1
Abstract: The swimming angle of larval Japanese anchovy (Engraulis japonicus) was measured in a tank, and target strength (TS) was calculated using a theoretical scattering model. The mean swimming angle was 12.8° (s.d. = ± 22.1). Increased speeds of flow led to increased mean swimming angles. The mean swimming angle at flow of 5 cm s^[-1] was higher than those at other speeds. TS values were estimated using a distorted-wave Born approximation model for two cases. Average values were 1-3 cm s^[-1] (Case 1: 11.5° ± 22.1) and 5 cm s^[-1] (Case 2: 16.6° ± 21.7) for cases 1 and 2, respectively. For case 1, TS ranged from -92.0 to -74.7 dB with a mean of -79.4 dB at 120 kHz. For case 2, TS ranged from -92.2 to -75.2 dB with a mean of -79.9 dB. The mean TS in case 2 was lower than that in case 1, with the maximum difference being 1.0 dB at 120 kHz [standard length 22.0 mm]. However, there were no significant differences between the regression lines of cases 1 and 2. Thus, changes in flow speed altered the swimming angle of larval Japanese anchovy, but had little influence on TS.
カタクチイワシシラスのような無鰾魚を対象に音響計測を実施する場合, わずかな姿勢角変化がターゲットストレングスに大きく影響する. 本研究では, 頭部を上向きにした状態で遊泳する傾向が強いこと(平均12.8°, 標準偏差±22.1), 流速が上昇するとこの傾向が強くなることを明らかにした. また, 分散分析により姿勢角結果を2ケースに分けTSを平均化したが, 両者にほとんど差はみられなかった. したがって, 物理環境により遊泳姿勢にわずかな違いが生じても, 標準偏差が高い場合は平均化TSへの影響は小さいと考えられた.
Rights: © 2011 公益社団法人日本水産学会
The final publication is available at www.springerlink.com
© 2011 The Japanese Society of Fisheries Science
Type: article (author version)
URI: http://hdl.handle.net/2115/45136
Appears in Collections:北方生物圏フィールド科学センター (Field Science Center for Northern Biosphere) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 宮下 和士

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