Effects of experimental otter trawling on the macrofauna of a sandy bottomecosystem on the Grand Banks of Newfoundland

A 3-year otter trawling experiment was conducted on a deepwater (120-146 m) sandy bottom ecosystem on the Grand Banks of Newfoundland that had not exp erienced trawling for at least 12 years. The benthic macrofauna were sample d before and after trawling and in reference areas. The 200 grab samples co llected contained 246 taxa, primarily polychaetes, crustaceans, echinoderms , and molluscs. Biomass was dominated by propeller clams (Cyrtodaria siliqu a) and sand dollars (Echinarachnius parma), while abundance was dominated b y the polychaete Prionospio steenstrupi and the mollusc Macoma calcarea. Th e most prominent feature of the data was a natural decline in the total num ber of species, the total abundance, and the abundance and biomass of selec ted species between 1993 and 1995. The only immediate effect of trawling wa s seen in 1994 when the abundance of 13 species, the biomass of 11 species (mostly polychaetes), and the total abundance per grab were significantly l ower. There was little evidence of long-term trawling effects. When trawlin g disturbance was indicated, it appeared to mimic natural disturbance, shif ting the community in the same direction in multidimensional scaling ordina tion; no distinctive trawling signature was observed. However, the results of this experiment should not be uncritically extrapolated to the impacts o f commercial trawling.