Abstract
This paper presents the current state of development and selected technological challenges in the application of ecologically and economically sustainable nets for aquaculture based on ongoing development projects. These aim at the development of a new material system of high-strength stainless steel wires as net material with environmentally compatible antifouling properties for nearshore and offshore aquacultures. Current plastic netting materials will be replaced with high-strength stainless steel to provide a more environmentally friendly system that can withstand more severe mechanical stresses (waves, storms, tides and predators). A new antifouling strategy is expected to solve current challenges, such as ecological damage (e.g., due to pollution from copper-containing antifouling substances or microplastics), high maintenance costs (e.g., cleaning and repairs), and shorter service life. Approaches for the next development steps are presented based on previous experience as well as calculation models based on this experience.
Highlights
The sometimes contradictory requirements for high strength with sufficient residual ductility for the manufacture of nets and, in particular, the corresponding corrosion resistance for use in seawater can best be met by the so-called corrosion-resistant duplex stainless steels (Figure 1)
Regardless of the degree of biological growth, this improves the living conditions of the fish. This positive condition is maintained by a continuous cleaning process, which leads to a higher sustainability
The use of nets made of high-strength and corrosion-resistant steel offers corresponding advantages over conventional nets made of plastic, from an ecological point of view, and subsequently from an economic point of view after a sufficient service life
Summary
Of the fish consumed worldwide, the total amount since 2016 has been more than 150 million tons per year, almost half is produced in aquacultures. To counteract the growth of undesirable organisms on the surface of man-made structures, better known as biofouling, these plastic nets are usually protected from fouling with anti-fouling agents These industrially available products are currently often made of copper and zinc. The application of copper-containing solutions to the net materials used is mainly by copper-containing dip coatings, which impregnates the nets This results in a continuous release of copper into the environment, causing the effects listed above to occur. Omitting the substances that protect against anti-fouling leads to a considerable reduction in the cross-section of the nets within a short time due to the colonization of algae, mussels or barnacles This fouling can adhere very well to conventional plastic nets and can only be removed with great technical effort, if at all. The state of the art, the development work carried out to date and the prospects are reported on below
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