Ecological management of biomass and metal bioaccumulation in fish-cage nettings: Influence of antifouling paint and fiber manufacture

Abstract

Biofouling causes major functional and economic problems for aquaculture due to their settlement and subsequent growth on fish-cage netting. As biofouling management is an economic and environmental issue, feasible management practices are clearly required to balance industries and environmental requirements. The most frequent way to control biofouling in aquaculture is by applying Cu-based antifouling paints on fish nets to prevent the undesired growth of biofouling. The most important fish species employed in marine fish farming are cultivated with knotted nylon and ultra-high-molecular-weight polyethylene (UW-polyethylene) nettings. In this study, we examined the effects of two commercial Cu coatings and two manufactured net materials (nylon and UW-polyethylene) on biofouling biomass, community structure, Cu bioaccumulation and the metal composition of fouling assemblages in order to provide farmers with a tool to help reduce the environmental impact of the biocide employed for coating nets. The MDS ordination of the samples coated with both paints on nylon and UW-polyethylene nets showed a gradual modification of community structure associated with rising Cu concentrations. The PCA analysis indicated that the ordination of trace element composition of biofouling varied between concentrations and nets in both paints. The experiments revealed that the fouling biomass decreased following negative exponential regression with an increasing Cu concentration. The increase in fouling biomass with reduced Cu bioaccumulation was greater in nylon than in UW-polyethylene nets. In the nylon nets, the median bioaccumulation on nets (CuF-50) rose with an 0.75- to 0.82-fold increase in the basal biomass. Conversely, biomass increased 0.50- to 0.63-fold the basal or minimum fouling biomass with a full antifouling paint concentration (B0) when CuF-50was calculated in the UW-polyethylene nets. These results suggest that similar reductions in bioaccumulated Cu in both nets could be achieved without sacrificing excessive fouling biomass increases.