Low-cost tool to reduce biofouling in oyster longline culture

In oyster longline aquaculture, biofouling leads to additional labour demands in order to clean the oyster containers and therefore an increase in 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 longlines positioned in an area of the Central Adriatic Sea protected by an artificial reef. The tool is mounted outside the traditional stack of oyster containers. Under the effect of sea currents and waves, it can freely and independently move around the external surface of the stackable containers. This results in the effective removal of biofouling without influencing the water flow inside the oyster trays. This device is applicable to many different types of underwater structure where a reduction of biofouling is required. Growth of the Pacific oyster spat, Crassostrea gigas (Thunberg, 1793), was studied over seven months. The oysters were cultured both in the traditional stacks and those treated by Wave-Brush. To test the effect of the Wave-Brush treatment on biomass of fouling taxa, a mixed-model permutational multivariate analysis of variance (PERMANOVA) was carried out. All test results from PERMANOVA analyses indicated unambiguously that faunal fouling assemblages on experimental containers were dissimilar to traditional ones even after few months. The Wave-Brush tool proved to 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.