Assessment of the performance of the RoxAnn (TM) acoustic ground discrimination system

The resolution, temporal variability and survey vessel speed dependence of the acoustic ground discrimination system RoxAnn(TM) was assessed over a 1 km(2) area in Loch Linnhe on the west coast of Scotland. The resolution of the system was relatively poor and of the sediment parameters quantified (stone cover and sediment texture), only stone cover was consistently and significantly related to the RoxAnn(TM) output. The output showed considerable variability over the same ground when sampled within the same day and between days and months. The effect of survey vessel speed on the output was also significant but highly variable during all surveys. The apparent magnitude and unpredictable nature of the variation in the RoxAnn(TM) output have implications for the use of such systems in habitat mapping, particularly when surveying biological communities where there are only small differences in the physical properties of the seabed and also where monitoring temporal change, These aspects are discussed. (C) 2003 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.