Acoustic classification of seabed habitats using the QTC VIEW™ system

The QTC VIEW™ acoustic seabed classification system was used in Frænfjorden, western Norway (62°N, 7°E), to map the spatial scales and variability of benthic habitats, and to evaluate its performance. Position and water depth were logged continuously along with the acoustic data. Water depth in the survey area ranged from 5 to 72 m over a spatial scale of ca. 1.5 × 8 km and there was considerable variation in sediment characteristics at 20 ground-truth sites. Six acoustically-distinct seabed types were identified and the QTC system defined their spatial scales and variability. Generally, the acoustic classifications were consistent at track crossings. The classification was generally in accordance with the sediment grain size and was most likely influenced by the softness of the substrate. However, these sediment characteristics could not alone explain the diversity of acoustic classes and the classes were probably also related to other physical or biotic seabed characteristics. The QTC system provides new insights but the usefulness of the acoustic classification depends upon the amount and quality of ground-truth data, which is the key aspect when relating acoustic class to seabed type. The acoustic system collects continuous data from large areas relatively quickly, and defines seabeds that would be missed by traditional core or grab point samples and will therefore be highly relevant to both geological- and benthic-diversity studies.