Distribution, abundance and acoustic properties of Antarctic

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TitleDistribution, abundance and acoustic properties of Antarctic silverfish (Pleuragramma antarcticum) in the Ross SeaAbstractAntarctic silverfish (Pleuragramma antarcticum) is a key link between plankton and the community of top predators in the shelf waters of the Ross Sea. In spite of their abundance and important role in Antarctic food chains, very little is known of many ecological and biological aspects of this species. A combined trawl and acoustic survey of silverfish was carried out on the western Ross Sea shelf during the New Zealand International Polar Year Census of Antarctic Marine Life research voyage on R.V. Tangaroa in February-March 2008. Multi-frequency acoustic data (12, 38, 70, and 120. kHz) allowed discrimination of silverfish marks from those of krill and other associated species. Mark identification was achieved using targeted midwater trawls. Additional midwater and demersal trawls were carried out at randomly selected locations over the shelf as part of the core biodiversity survey. Silverfish were widely distributed over the Ross Sea shelf. Adult silverfish tended to form layers at 100-400. m depth and were sometimes present close to the bottom, where they were frequently caught in demersal trawls shallower than 500. m. A weak layer at about 80. m depth was associated with juvenile silverfish of 50-80. mm standard length. Acoustic backscatter strength from both silverfish and krill marks increased with increasing frequency (i.e., was highest at 120. kHz), which is characteristic of species without an air-filled swimbladder. Acoustic target strengths (TS) for silverfish at 12, 18, 38, 70, and 120. kHz were estimated from anatomically detailed scattering models based on computed tomography (CT) scans of frozen specimens. The relationship between TS and fish length at 38. kHz was sensitive to estimates of density and sound speed contrast within the fish, especially for small specimens (less than 110. mm SL). Our best estimate of the acoustic biomass of silverfish in the study area was 592. 000. t (95% confidence interval 326. 000-866. 000. t). However, the biomass of juvenile silverfish was highly uncertain due to large differences between TS model results. â"' 2010 Elsevier Ltd.AcknowledgementsWe thank the officers, crew, and scientific staff on R.V. Tangaroa for their hard work, experience, and professionalism before, during, and after the survey. We are very grateful to Chris Francis for statistical advice on estimation of survey uncertainties, to Jennifer Devine for her comments on the draft manuscript, and to Brent Wood for drafting Figs. 1, 3, and 6. The manuscript was improved following reviews by Marino Vacchi, Mario La Mesa and Joseph Eastman. This research was funded by the New Zealand Government under the New Zealand International Polar Year Census of Antarctic Marine Life Project (Phase 1: So001IPY; Phase 2: IPY2007-01). We gratefully acknowledge project governance by the Ministry of Fisheries Science Team and the Ocean Survey 20/20 CAML Advisory Group (Land Information New Zealand, Ministry of Fisheries, Antarctica New Zealand, Ministry of Foreign Affairs and Trade, and National Institute of Water and Atmosphere Ltd). This is CAML contribution #35.

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1st AuthorO'Driscoll, R. AuthorO'Driscoll, R. Macaulay, G.Gauthier, S.Pinkerton, M.Hanchet, S.Year2011JournalDeep-Sea Research Part II: Topical Studies in OceanographyVolume58Number1/02/2017Pages181-195DOI10.1016/j.dsr2.2010.05.018URLhttps://www.scopus.com/inward/recor.....e77b3036f55c1e933968e771aKeywordsAbundanceAntarcticaEcho surveysForage fishRoss SeaTarget strength, Acoustic propertiesBiodiversityComputerized tomographyEcologyFishFisheriesSurveys, Geographical distribution, abundanceadultbioacousticsbiomasscensuscontinental shelfcrustaceandata setfood chaingeographical distributionjuvenileperciformpopulation distributiontomographytrawling, Ross SeaSouthern Ocean, Decapoda (Crustacea)EuphausiaceaPleuragramma antarcticum, rank5Author KeywordsAbundanceAntarcticaEcho surveysForage fishGeographical distributionRoss SeaTarget strength

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TypeArticleCitationO'Driscoll, R., Macaulay, G., Gauthier, S., Pinkerton, M. and Hanchet, S. (2011) Distribution, abundance and acoustic properties of Antarctic silverfish (Pleuragramma antarcticum) in the Ross Sea. Deep-Sea Research Part II: Topical Studies in Oceanography, 58(1-2): 181-195 doi:10.1016/j.dsr2.2010.05.018