SG-ASAM-09

Acoustic target classification protocols recently adopted by utilising the Stochastic Distorted Wave Approximation (SDWBA) krill target strength model, are assessed. Three frequency acoustic data and concurrent net information, from 16 net hauls through krill aggregations, were collected during two cruises to the South Georgia region in 1996. For each net-sampled aggregation the differences Read More
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During February and March 2008 New Zealand carried out a major research voyage into the Ross Sea region in support of the International Polar Year Census of Antarctic Marine Life (IPY-CAML). The 50 day voyage on the research vessel Tangaroa involved an extensive survey of marine organisms from viruses to pelagic and demersal fish and cephalopods in depths from the surface down to 3500 m, and Read More
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An anatomically detailed acoustic scattering model has been used to estimate the backscattered target strength (TS) of six mackerel icefish (Champsocephalus gunnari) of total length 26.8–35.0 cm, at 38 kHz. The model used computed tomography (CT) scans of fish to determine the sound speed and density throughout the fish and simulated the complex interaction of the incident sound wave with the Read More
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The spatial distribution characteristics of ice-fish in the near-bottom layer are analyzed using the acoustic data obtained in the South Georgia area during the Russian bottom trawl surveys 2002. Acoustic and trawl density samples obtained in the near-bottom layer covered by trawl survey are compared. It is shown the possibility to estimate the bottom trawl efficiency. The high heterogeneity Read More
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Fishery for krill is a major economical activity in the Antarctic Ocean. The increased Norwegian fishery inherently gives Norway a responsibility to contribute to the management of the marine resources in the southern ocean. During the International Polar Year 2008, RV “G.O. Sars” spent 3 months in the Antarctic Ocean to do investigations on euphausiids and other key components of the Read More
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In order to describe an aquatic ecosystem scientists require a variety of information. Some of this information can be obtained using underwater acoustics. As examples acoustics is often used to provide information about biomass densities, biological species compositions, size distributions, behavior in space and time, and links to other environmental information such as habitats. Examples of Read More
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Target strength (TS) determinations can be classified into several types: 1) theoretical, 2) ex situ measures on dead or living fish under experimental conditions, 3) in situ measures on free swimming fish in their natural habitat. A canvassing of the literature suggested that the type of study may influence the result. For example, some authors suggested that freezing the fish reduce the over Read More
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A submersible multifrequency acoustic TS-probe was used for measuring the target strength of Antarctic krill in situ at short range. The experimental methods, procedure for data retrieval and analysis with some results for one selected station are presented. A Simrad EK60 split beam system operating at 38, 120 and 200 kHz is installed in the probe, connected to three pressure resistant Read More
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