Experimental low-cost tool to reduce biofouling in oyster longline culture

Biofouling represents an important problem in oyster longline aquaculture because it leads to additional labour in order to clean the oyster containers; therefore it increases the time and costs for the maintenance of the longline system. To deal with these problems a low-cost prototype tool, named Wave-Brush, was developed, patented and tested for a short period of time on Central Adriatic Sea longlines. The experimented tool is mounted outside the traditional stack of oyster containers. The effect of sea currents and waves makes the tool able to move freely and independently around the external surface of the stackable containers. The brushing movement results in the effective removal of biofouling without influencing the water flow inside the oyster trays. This device could be applicable to many different types of underwater structure where a reduction of biofouling is required. In the current study the growth of the Pacific oyster spat, Crassostrea gigas (Thunberg, 1793), was studied over seven months. The oysters were cultured both in the traditional and experimental (treated by Wave-Brush) stacks. A mixed-model permutational multivariate analysis of variance (PERMANOVA) was carried out in order to test the effect of the Wave-Brush treatment on biomass of fouling taxa,. All test results from PERMANOVA analyses clearly indicated that faunal fouling assemblages on experimental containers were very different from traditional ones even after few months. The Wave-Brush tool could be an easy, inexpensive and useful tool to improve performance and allow oyster culture in eutrophic waters. In particular, Wave-Brush substantially reduced the biofouling and mussel settlement on the oyster containers.