caa a22 4500 39755043X CHVBK 20180308164748.0 cr unu---uuuuu 161202e199604 xx s 000 0 eng 10.1006/jmsc.1996.0039 doi (NATIONALLICENCE)oxford-10.1006/jmsc.1996.0039 Swimming behaviour and target strength of isada krill (Euphausia pacifica) [Elektronische Daten] [Kazushi Miyashita, Ichiro Aoki, Tadashi Inagaki] The swimming angle of isada krill (Euphausia pacifica Hansen) was measured in a tank and the target strength (TS) values were calculated using a theoretical scattering model. The average swimming angle was 30.4° (s.d.=19.9°), which was about 15° less than that reported for Antarctic krill (Euphausia superba). Parameters for the swimming angle distribution were substituted into the straight cylinder model and the corresponding TS values were determined. The mean TS values of 16.4 mm isada krill for hovering animals were lower than the maximum TS; differences were 7.8-5.0 dB, 14.8-8.6 dB, and 18.1-10.8 dB at 50, 120, and 200 kHz, respectively. These differences will lead to a 1/6-1/3, 1/30-1/7, and 1/65-1/12 proportional difference, respectively, in estimating abundances compared to estimates based on the maximum TS. Measurements carried out at higher frequencies are more influenced by swimming angle than those at lower frequencies. However, the TS is less at lower frequencies and it is more difficult to filter out noise. Thus, medium frequencies are suggested as the best for krill surveys. Additionally, when conducting resource surveys by echosounding, it is necessary to assign the appropriate swimming angles for different targets. Swimming angles need to be investigated further under a variety of conditions. © 1996 International Council for the Exploration of the Sea Regular Articles nationallicence Euphausia pacifica nationallicence swimming angle nationallicence target strength nationallicence theoretical scattering model nationallicence Miyashita Kazushi Division of Fisheries Ecology Ocean Research Institute, University of Tokyo, 1-15-1, Minamidai, Nakano-ku, Tokyo 164, Japan aut Aoki Ichiro Division of Fisheries Ecology Ocean Research Institute, University of Tokyo, 1-15-1, Minamidai, Nakano-ku, Tokyo 164, Japan aut Inagaki Tadashi Division of Fisheries Ecology Ocean Research Institute, University of Tokyo, 1-15-1, Minamidai, Nakano-ku, Tokyo 164, Japan aut ICES Journal of Marine Science Oxford University Press 53/2(1996-04), 303-308 1054-3139 53:2<303 1996 53 icesjms https://doi.org/10.1006/jmsc.1996.0039 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1006/jmsc.1996.0039 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Miyashita Kazushi Division of Fisheries Ecology Ocean Research Institute, University of Tokyo, 1-15-1, Minamidai, Nakano-ku, Tokyo 164, Japan aut NATIONALLICENCE 700 1- Aoki Ichiro Division of Fisheries Ecology Ocean Research Institute, University of Tokyo, 1-15-1, Minamidai, Nakano-ku, Tokyo 164, Japan aut NATIONALLICENCE 700 1- Inagaki Tadashi Division of Fisheries Ecology Ocean Research Institute, University of Tokyo, 1-15-1, Minamidai, Nakano-ku, Tokyo 164, Japan aut NATIONALLICENCE 773 0- ICES Journal of Marine Science Oxford University Press 53/2(1996-04), 303-308 1054-3139 53:2<303 1996 53 icesjms Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford