Limited infaunal response to experimental trawling in previously untrawledareas

There is considerable argument about the effects of bottom trawling on the benthos. Many studies have been done on recently trawled grounds, where com munity composition has already been modified, and further effects are likel y to be minimal. This study tests the effect of trawling on macroinfaunal a ssemblages in an area where little or no trawling had occurred in the previ ous 15 years. A spatially replicated Before-After, Control-Impact (BACI) de sign was used, with adjacent trawl and control corridors. Sampling was done in the same two small sites within each corridor before and after trawling to minimise confounding due to spatial variation. Despite this rigorous de sign, changes consistent with an effect of trawling were not detected. At o nly one of the three locations was a potential effect detected. These incon sistent results could be due to different disturbance regimes at each locat ion, influencing the vulnerability of fauna to further disturbance. Given t he high levels of variability in infaunal assemblages, however, the changes could also be due to asynchronous natural variation. The combination of hi gh spatial and temporal variability, in association with light trawling gea r, means that prawn trawling in South Australia does not have consistent ef fects on infauna. (C) 2001 International Council for the Exploration of the Sea.