Macroinvertebrate community responses to clam aquaculture practices in British Columbia, Canada

Despite recent growth of shellfish aquaculture in B.C., Canada, very little is known regarding impacts of common practices. Seeding and netting are frequently employed on clam farms to increase production of' Venerupis philippinarum. A pilot netting experiment found no observable effect of predation at small scales. A field study compared bivalve communities on clam farms with matched reference sites, using density and biomass data. V, philippinarum was the only species found in higher abundance on farm sites, consistent with values expected from clam seeding. Bivalve communities were not significantly different on farm sites, but were more similar on average than reference sites, leading to a loss of regional distinctness. These results are consistent with recent research suggesting that predation and competition may play minor roles in structuring communities in soft-bottom environments. Given the remaining uncertainties, a precautionary approach is recommended in future development of the intertidal for clam aquaculture.