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An investigation of avoidance by Antarctic krill of RRS James Clark Ross using the Autosub-2 autonomous underwater vehicle |
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| Authors: | Andrew S Brierley Paul G Fernandes Mark A Brandon Frederick Armstrong Nicholas W Millard Steven D McPhail Peter Stevenson Miles Pebody James Perrett Mark Squires Douglas G Bone Gwyn Griffiths |
| Institution: | a British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK b FRS Marine Laboratory Aberdeen, P.O. Box 101, Victoria Road, Aberdeen AB11 9DB, UK c Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK d Southampton Oceanography Centre, Empress Dock, Southampton SO14 3ZH, UK |
| Abstract: | The autonomous underwater vehicle (AUV) Autosub-2 was deployed on eight missions ahead of RRS James Clark Ross in the northern Weddell Sea and in the Bransfield Strait, Southern Ocean, to assess avoidance of the research vessel by Antarctic krill Euphausia superba. The AUV was equipped with the same type of scientific echosounder as the research vessel (Simrad EK500 operating at 38 and 120 kHz) and measured the density of krill along transect acoustically (g m?2 wet mass) prior to the ship’s arrival. We hypothesised that if krill avoided the ship, perhaps in response to radiated noise, then the ship should detect less krill than the AUV which is known to have much lower noise levels than the ship. We were unable to detect any significant difference between the density of krill detected by the ship or the AUV, either at the transect level or at finer scales within transects. We conclude, therefore, that avoidance by krill of RRS James Clark Ross will not significantly bias acoustic estimates of krill abundance by this vessel. |
| Keywords: | Acoustic survey Avoidance Autosub Antarctic krill Biomass estimate Euphausia superba Vessel noise |
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