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 acoustic impedance contrasts throughout the fish. A preliminary length to tilt-averaged TS relationship is derived from the model results: 148)(log4.7010-=LTSwhere L is the fish total length in cm and is applicable to fish of length 26–35 cm. Existing in situ TS estimates are for smaller fish (16–26 cm) and hence are not directly comparable, but extrapolation of the in situ and model results reveal a large different in TS (6 dB at 26 cm) between the two datasets.
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There is no abstract available for this document.
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Abstract:
Due to current uncertainties in the status of Antarctic krill biomass stock, which do not allow scientists to provide a work on forecast of the ecosystem changes and provide the management advice on SSMU catch limit allocation subdivision, that has been mentioned at the WG on Ecosystem Monitoring and Management Meeting, Bergen 2009, it is proposed to consider the changes to Conservation Measure 51-01 (2008) accepting as interim protection measure the trigger level allocation between statistical Subareas in statistical area 48 for krill fishery.
