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  1. No Access

    Article

    Volume backscattering spectra measurements of Antarctic krill using a broadband echosounder

    For the acoustic inference of lengths and orientation angles of Antarctic krill (krill), reliable theoretical acoustic scattering models and parameters are necessary. To measure the volume backscattering (SV) ...

    Natsuki Yamamoto, Kazuo Amakasu, Koki Abe, Ryuichi Matsukura… in Fisheries Science (2023)

  2. No Access

    Article

    Effects of fast Fourier transform window size on the target strength spectra of tungsten carbide spheres

    The window size (WS) of the fast Fourier transform (FFT) is one of the important parameters when calculating target strength (TS) spectra from broadband echo waveforms. However, the effects of the FFT WS on TS...

    **g Liu, Burak Saygili, Akira Iwasa, Natsuki Yamamoto… in Fisheries Science (2023)

  3. No Access

    Article

    Estimated ammonium regeneration potentials of two common euphausiid species (Euphausia superba and E. crystallorophias) off Adélie Land, East Antarctica, in austral summer, 2008

    Zooplankton contribute to nitrogen regeneration for primary productivity via ammonium excretion. To improve our understanding of the biogeochemical role of zooplankton in the Southern Ocean, ammonium excretion...

    Atsushi Ono, Fuminori Hashihama, Kazuo Amakasu, Masato Moteki in Polar Biology (2022)

  4. No Access

    Article

    Annual variation of oceanographic conditions changed migration timing of bowhead whales Balaena mysticetus in the southern Chukchi Sea

    The Chukchi Sea environment changes considerably in physical and biological conditions, driven by the expanding volume of warm Pacific summer water. These environmental changes can affect the migration timing ...

    Koki Tsujii, Mayuko Otsuki, Tomonari Akamatsu, Kazuo Amakasu… in Polar Biology (2021)

  5. No Access

    Article

    A broadband target strength measurement method for weakly scattering animals using a 50-ms-long linear frequency modulated signal in a small tank

    We built a new pulse-echo system using a small tank (1 × 1 × 1 m) for measuring the broadband target strength of weakly scattering animals such as krill and shrimp. The system transmits a linear frequency modu...

    Burak Saygili, Soma Tsuyuki, **g Liu, Natsuki Yamamoto… in Fisheries Science (2021)

  6. No Access

    Article

    Estimation of target strength of Sardina pilchardus and Sardinella aurita by theoretical approach

    The target strength (TS) patterns of Sardina pilchardus and Sardinella aurita at 38 and 120 kHz were estimated by a prolate-spheroid model, using measurements of swimbladder length and width. The ratio of swimbla...

    Salaheddine El Ayoubi, Kamal Mamza, Tadanori Fu**o, Koki Abe… in Fisheries Science (2016)

  7. No Access

    Article

    Basin-scale distribution pattern and biomass estimation of Japanese anchovy Engraulis japonicus in the western North Pacific

    The distribution pattern and biomass of the Japanese anchovy Engraulis japonicus in the offshore region of the western North Pacific (north of 35°N and west of 170°E) were studied using a quantitative echosounder...

    Hiroto Murase, Atsushi Kawabata, Hiroshi Kubota, Masayasu Nakagami… in Fisheries Science (2012)

  8. No Access

    Article

    Multilayer biological structure and mixing in the upper water column of Lake Biwa during summer 2008

    We carried out a 24-h station experiment at Lake Biwa (Japan) to measure mixing events and concurrent biological signals using a free-fall microstructure profiler (TurboMAP-L), conventional hydrographic measur...

    Hidekatsu Yamazaki, Hikaru Honma, Takeyoshi Nagai, Mark J. Doubell… in Limnology (2010)

  9. No Access

    Article

    Pelagic fish distribution and ontogenetic vertical migration in common mesopelagic species off Lützow-Holm Bay (Indian Ocean sector, Southern Ocean) during austral summer

    The horizontal and vertical distributions of fish were examined off Lützow-Holm Bay in the Indian Ocean sector of the Southern Ocean during midnight sun in January 2005. Fish were sampled from six discrete dep...

    Masato Moteki, Naho Horimoto, Riou Nagaiwa, Kazuo Amakasu… in Polar Biology (2009)

  10. No Access

    Article

    Measurement of sea bottom surface backscattering strength by quantitative echo sounder

    Measurement theory and method of the bottom surface backscattering strength (SS) using a quantitative echo sounder (QES) are discussed and applied in the ocean near Java, Indonesia. The frequencies of the QES ...

    Henry Munandar Manik, Masahiko Furusawa, Kazuo Amakasu in Fisheries Science (2006)