Mapping seabed biotopes using sidescan sonar in regions of heterogeneous substrata: Case study east of the Isle of Wight, English Channel

History of benthic research in the English Channel: From general patterns of communities to habitat mosaic description

“…At the same time, the research on aggregates and their extraction gave rise to renewed interest in benthic studies integrating the need for knowledge of aggregate resources and the impact of extraction on benthic habitats (Arnal et al, 1985;Dauvin, 1997). This provided the opportunity to develop new techniques for benthic observations (Birchenough et al, 2010;Brown et al, 2002Brown et al, , 2004aBrown et al, ,b, 2011Cooper, 2012Cooper, , 2013Eastwood et al, 2007;Foster-Smith et al, 2004;Le Bot et al, 2010).…”

“…Before, Holme and Wilson (1985) used sonar and television to determine the benthic assemblages of the central EC to the south of the Isle of Wight. Subsequently, the CEFAS promoted this type of integrated approach on the English side of the Channel especially to study the pattern of mixed soft-hard bottoms (see Brown et al, 2002Brown et al, , 2004aBrown et al, ,b, 2011. The 'REseau BENthique' (REBENT programme has also studied benthic habitats using several techniques around the Brittany coast, including sidescan sonar and grab sampling.…”

“…Mainly for the areas of aggregate extraction in the EC, the CEFAS team developed an integrated approach (Brown et al, 2002(Brown et al, , 2004a using both sidescan sonar and grab sampling to map a variety of benthic biotopes as well as their distribution, i.e. seabed habitats and their associated biological communities.…”

Mapping seabed habitats in the Firth of Lorn off the west coast of Scotland: evaluation and comparison of habitat maps produced using the acoustic ground-discrimination system, RoxAnn, and sidescan sonar

“…swathe acoustic systems) should be used instead. It is important to recognize though that habitat boundaries are not always discrete, and the issue of boundary placement can be very problematic, particularly in soft sediment regions where boundaries can be ''fuzzy'' or in areas of very heterogeneous substrates where small-scale patchiness can cause problems delineating discrete habitats (Brown et al, 2004b). Concerns were raised during the workshop that the study area was too small and too heterogeneous to make a fair assessment of the ability of AGDS to map seabed habitats.…”

Remote identification of a shipwreck site from MBES backscatter

“…These techniques have also been used to attempt to extract different properties from the backscatter data, including physical (i.e., porosity), acoustic (attenuation), or geotechnical (elastic and shear strength moduli) properties, and also the general morphology at different scales Hughes Clarke et al, 1993;Mayer, 2011;Mayer et al, 2007). Backscatter information has also been used for identification of regions with similar acoustic properties e called acoustic themes e defined using conventional, subjective interpretation, although this approach is less effective for seafloor with a high level of seabed heterogeneity or a gradual change in the seabed characteristics (Brown and Collier, 2008;Brown et al, 2004). The dependence of the backscattered energy on the material types (among other factors), however, suggests that it might be appropriate for characterization of anthropogenic objects.…”