The effect of floating bag management strategies on biofouling, oyster growth and biodeposition levels

Commerically-viable aquaculture of the Eastern oyster (Crassostrea virginica) in New Brunswick. Canada, depends on optimizing production strategies during the short growing season while minimizing environmental impacts. Fouling levels oil the floating bags used for oyster culture are typically controlled by Periodic turning in order to expose the accumulated biomass to air drying. The impact of different bag turning frequencies on fouling levels, oyster production, biodeposition rates and the settlement of fouling species was assessed at two sites in northern New Brunswick. Over the 4 month study period (June-October 2006) the fouling biomass increased exponentially to a maximum of 300 g dry wt. for bags which were never turned. Maintenance activity aimed at reducing fouling levels did not, however, enhance oyster performance: growth and Survival rates were similar in bags turned bi-weekly, monthly, once in mid-August or never. Biodeposition rates Under the bags were also similar among handling treatments and did not significantly exceed reference levels even immediately following bag turning events. With regard to Fooling control, bag turning Was effective in eliminating the settlement of barnacles and mussels on the hags, but not oil the oysters. In general, given the current fouling community, turning floating bags once in mid-August following the barnacle settlement in late July would likely be sufficient to control most species. Ongoing mussel settlement doling September may, however, necessitate one additional handling in early october prior to sinking of the bags for the winter. (C) 2008 Elsevier B.V. All rights reserved.