Abstract only. Journal home page: http://scitation.aip.org/jasa

Anderson, Cairistiona I.H.

Godø, Olav Rune

Horne, John K.

Patel, Ruben

English

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11:251aAOa2. Effects of scattering layer composition, animal size, and numerical density on the frequency dependence of volumebackscatter. Kelly Benoit-Bird College of Oceanic and Atmospheric Sci., Oregon State Univ., Corvallis, OR 97331The mesopelagic boundary community around the Hawaiian Islands is a land-associated, sound scattering layer that undergoes dielmigrations with both a vertical and horizontal component. A video camera system was developed to quantitatively examine thenumerical density, size, and taxonomic composition of micronekton. The camera system was combined with a four-frequencyvessel-mounted echosounder system 38, 70, 120, and 200 kHz to document the full migration range of micronekton and describe thechanges in composition and density throughout their diel migration. Migrating animals split into multiple, distinct layers at night withdifferences in micronekton density, composition, and size. These differences were correlated with differences in the frequencyresponse of volume backscatter. The relationship between these variables and backscatter intensity relationship between frequencies iscomplex. The results suggest strong partitioning of habitat by these animals in space and time, which, along with the high densitiesof animals, indicate that competition is important in driving the behavior and structuring the community.11:451aAOa3. Probing the deep: Acoustic characterization of the Mid-Atlantic Ridge ecosystem. John K. Horne, Cairistiona I. H.Anderson School of Aquatic and Fishery Sci., Univ. of Washington, Box 355020, Seattle, Wa 98195, Olav Rune Godoe, andRuben Patel Inst. of Marine Res., Nordnes 5817, Bergen, NorwayImplementation of the ecosystem approach to resource management potentially increases the use of acoustics during assessmentsurveys. A Census of Marine Life survey on the mid-Atlantic ridge during summer 2004 was an opportunity to develop a practicalapproach. The Norwegian vessel, G. O. Sars, is an acoustically-quieted platform equipped with a five-frequency 18, 38, 70, 120, and200 kHz echosounder, acoustic Doppler current profilers ADCPs, multibeam sonars, and a deep-towbody. Paucity of information onspecies composition limited the ability to conduct a traditional acoustic survey. Acoustic structure independent of biological samplingwas quantified and then integrated acoustic density and target strength observations with biological community composition andlength frequency data. Species were not assigned backscatter thresholds or water column regions at the onset of analysis. Near-real-time products monitored biomass distributions: daily echograms, target strengths, and frequency-differenced echograms. Persistentbiological layers at different depths occurred in the water column. Layers or components migrated toward the surface during darkhours. Modes of target strength frequency distributions and trawl catch compositions differed among layers. The use of acoustic andnet technologies can be integrated with near-real-time analytic results to quantitatively characterize pelagic ecosystems. Worksupported by ONR, IMR, and NOAA Fisheries.TUESDAY MORNING, 28 NOVEMBER 2006 KAUAI ROOM, 11:00 A.M. TO 12:05 P.M.Session 1aAObAcoustical Oceanography and Signal Processing in Acoustics: Acoustic Tomography for Coastal and DeepWater Applications IJames A. Mercer, CochairUniv. of Washington, Applied Physics Lab., 1013 NE 40th St., Seattle, WA 98105-6698Arata Kaneko, CochairHiroshima Univ., Graduate School of Engineering,1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8527, JapanChair’s Introduction—11:00Invited Papers11:051aAOb1. Current structure measurements by the coastal acoustic tomography. Arata Kaneko, Keisuke Yamaguchi, Ju Lin,Noriaki Gohda Grad. School of Eng., Hiroshima Univ., 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan, HongZheng SEA Corp., Ichikawa, Chiba 272-0127, Japan, and Yoshio Takasugi Chugoku Ctr. of Natl. Inst. of Adv. Industrial Sci. andTechnol., Kure, Hiroshima 737-0197, JapanThe coastal acoustic tomography CAT, coastal-sea application of deep-sea acoustic tomography Munk and Wunsch, 1978, isproposed as an advanced technology to map current structures in the coastal sea. A sequence of successful experiments was recentlycarried out in the coastal seas with various oceanographic conditions around Japan Yamaguchi et al., 2005; Kaneko et al., 2005; Linet al., 2005. In the Tokyo Bay experiment of November 2002, the 2-D tidal currents inducing a clockwise residual circulation weremapped by eight CAT systems, located at both the eastern and western coasts of the bay. The vortex-embedded tidal currents with amaximum velocity of 5 ms1 were targets in the Kanmon Strait experiment of March 2003. In the Hiroshima Bay experiment of1aTUE.AM3001 3001J. Acoust. Soc. Am., Vol. 120, No. 5, Pt. 2, November 2006 Fourth Joint Meeting: ASA and ASJ

Probing the deep: Acoustic characterization of the Mid-Atlantic Ridge ecosystem

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Probing the deep: Acoustic characterization of the Mid-Atlantic Ridge ecosystem

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