Technological Approaches to Longline- and Cage-Based Aquaculture in Open Ocean Environments

Abstract

As the worldwide exploitation rate of capture fisheries continues, the development of sustainable aquaculture practices is increasing to meet the seafood needs of the growing world population. The demand for aquatic products was historically satisfied firstly by an effort to expand wild catch and secondly by increasing land-based and near-shore aquaculture. However, stagnation in wild catch as well as environmental and societal challenges of land-based and near-shore aquaculture have greatly promoted efforts to development farming offshore technologies for harsh, high energetic environments. This contribution thus highlights recent technological approaches based on three sample sites which reach out from sheltered near-shore aquaculture sites to sites with harsh wave/current conditions. It compares and evaluates existing technological approaches based on a broad literature review; on this basis, we then strongly advocate for presently available aquaculture technologies to merge with future offshore structures and platforms and to unveil its added value through synergetic multi-use concepts. The first example

Physical Modelling of Blue Mussel Dropper Lines for the Development of Surrogates and Hydrodynamic Coefficients

“…Each specimen, though differing in total length, was submerged over a length of Lwet = 0.80 m. This, in turn, allows the correct determination of the drag coefficient for a specified length of mussel dropper line. The Reynolds numbers = * ⁄ covered during the tests were determined with the characteristic diameter = 10.31 cm , the aforementioned towing velocities , the kinematic viscosity of the water ν = 1.004/998,200 [m²/s] and the constant water temperature of 20 °C and range from 2.0 × 10 4 to 1.1 × 10 5 . In between all drag tests, the flow disturbances potentially induced by previous testing settled during a waiting period in order to avoid biased influence.…”

“…Especially at offshore sites, high energy is acting on the structures as a result of wave and current conditions. Although hydrodynamic forces acting on fixed and floating structures in such conditions are commonly investigated, existing research related to shellfish aquaculture is generally limited [5]. The feasibility of moving bivalve-related aquaculture offshore is mainly evaluated in regard to farming techniques that are already in use.…”

Potential Effects of Climate Change on Offshore Aquaculture of the Mediterranean Mussel (Mytilus galloprovincialis, Lamarck, 1819) in Portugal

“…Institutions responsible for the governance of aquaculture in Portugal should also look at how other countries, such as New Zealand, have developed successful offshore aquaculture over a relatively short time period. Long-term funding (7 y) is provided to the industry in collaboration with researchers to resolve any problems affecting the industry (Goseberg et al 2017, Newell et al 2021).…”

Potential for Coastal and Offshore Aquaculture in Portugal: Insights from Physico-Chemical and Oceanographic Conditions

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