Determining sediment properties around a marine cage farm using acoustic ground discrimination: RoxAnnTM

Sediment traps collected significant quantities of waste solids beneath marine fish cages at a fish farm site in Greece. Diver observation and the absence of dissolved hydrogen sulphide in the water overlying sediments revealed low benthic impacts despite the very low current speeds measured. An acoustic bottom discrimination system, ground-truthed by conventional remote photography, further confirmed the apparently low benthic impact at this site. These results may be explained partly by the large number of fish present around the cages feeding on farm wastes.