THE EFFECT OF BIOTURBATION ON ROXANN(R) A REMOTE ACOUSTIC SEABED DISCRIMINATION SYSTEM

Whilst evaluating the use of RoxAnn(R) for benthic biotope mapping it was noted that over certain visually similar sediments differences wer e observed in the acoustic signature. To assess this phenomenon a numb er of physical parameters were determined (mean sediment grain size, s ediment sorting, sediment organic carbon content and the percentage of sand, silt and clay present in the substratum) from within a survey a rea in the North Minch. Investigation of the epifaunal and burrowing m egainfaunal communities was also carried out using towed underwater te levision (TV) techniques. Generalized linear modelling showed that cha nges in Nephrops norvegicus burrow density could account for 94.7% of the variability in the RoxAnne(R) E1 signal. The model, however, appea red to be improved when both the percentage of silt present and the so rting of the sediment were also taken into account, with 98.1% of the variance in E1 being explained. Although improving the original model, the addition of these extra variables was, however, considered insign ificant in terms of the variability accounted for by N. norvegicus den sity alone. The findings of this study are discussed in relation to po ssible shellfish management.