The effects of experimental scallop dredging on the infaunal benthic community structure of Port Phillip Bay, using a BACI design, has been investigated by Currie and Parry (1996). The abundances of seven of the 10 most common species changed significantly, with six decreasing and only one increasing. Dredging impacts varied among species, but in general most species initially decreased in abundance by 20 to 30% then recruited within six months of the dredging impact (after which impacts became undetectable). A small number of species, however, still had not recruited after 14 months and appeared to be responsible for a persistent change in community structure. The general conclusion was that scallop dredging had profound impacts on the benthos and probably cannot be sustained (see also Section 6.3.2). In the US, Thrush et al. (1995) conducted field experiments to test the short-term impacts of commercial scallop dredging on macrobenthic communities. Dredging decreased the density of common macrofaunal populations, and resulted in significant compositional changes, with some differences still apparent three months later. These findings were considered to provide a conservative assessment of the impact from dredging.

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Department of Environment and Heritage