Photographic evidence of the importance of macrofauna in the removal of feed pellets from the sediment under marine salmon farms

Photographic evidence was collected demonstrating that epibenthic macrofauna were capable of removing, in less than 7 days, fish feed pellets spread at a density of 3.4 kg dry wt. per m² on the sediment under a marine fish farm. The use of wire mesh cages laid over the pellets demonstrated that the majority of the removal was accomplished by animals capable of passing through a 7.5 cm² mesh but not a 2.5 cm² mesh. Visual evidence suggested that green crabs (Carcinus maenas) may have been one of the dominant species involved in processing the pellets. It is argued that these observations may provide one explanation of the low amounts of oxytetracycline that have been reported to be present in the under-cage sediments.