@article{oai:nipr.repo.nii.ac.jp:00010229,
 author = {Amakasu, Kazuo and Ono, Atsushi and Moteki, Masato and Ishimaru, Takashi and Amakasu, Kazuo and Ono, Atsushi and Moteki, Masato and Ishimaru, Takashi},
 issue = {2},
 journal = {Polar science, Polar science},
 month = {Aug},
 note = {Sexual dimorphism in the body shape of Antarctic krill (Euphausia superba) was investigated and its influence on target strength (TS) was clarified using a theoretical scattering model. The TS which is used to convert acoustic backscatter to krill density was also presented. Body shape data were obtained from 456 specimens (54 juveniles, 200 males, and 202 females) collected off Adélie Land using a Rectangular Midwater Trawl. The sexual dimorphism manifested as a swollen cephalothorax in female krill with body lengths exceeding 40 mm. The TS of female krill was higher than those of male krill at low frequencies, even when body lengths were the same. This is because of the Rayleigh scattering region and the transition region to the geometric scattering region. The influence of the sexual dimorphism on the TS was small at frequencies exceeding 70 kHz, which are close to the geometric scattering region. The regression curve derived from the predicted TS of 456 specimens was in reasonable agreement with the measured TS in other previous studies, and the regression curve could be applied to the acoustic surveys of Antarctic krill., ナンキョクオキアミ（Euphausia superba）の体形状の雌雄差を調べ，それがターゲットストレングス（TS）へ与える影響について理論散乱モデルを使用して明らかにした。また，音響散乱強度からオキアミ密度へ換算するために使用するTSも示した。体形状は，アデリーランド沖においてRectangular Midwater Trawlによって採集した456個体（ジュベニル54個体，オス200個体，メス202個体）から得た。体長40 mmを超えるメスは頭胸部の膨らみが顕著であり，雌雄差として見られた。低周波においては，同じ体長であってもメスの方がオスよりもTSが高かった。これはレイリー散乱領域や幾何散乱領域への遷移領域に相当するからである。幾何散乱領域に近づく70 kHz以上では，TSへの雌雄差の影響は小さかった。理論散乱モデルによって推定した456個体のTSから求めた回帰曲線は，他の先行研究におけるTSの実測値と一致しており，ナンキョクオキアミの音響調査に使用することができた。},
 pages = {179--186},
 title = {Sexual dimorphism in body shape of Antarctic krill (Euphausia superba) and its influence on target strength},
 volume = {5},
 year = {2011}
}