Description: Drawing on a case study in Germany, this contribution explores the practical application of offshore aquaculture within offshore wind farms in view of the different stakeholders involved. Using a transdisciplinary research approach, an understanding of the rationalities and interests among the different involved stakeholder groups was explored. Offshore wind energy is high on the political agenda in Germany. The vast spatial requirements however inherit potential user conflicts with competing, and under current legislation excluded users such as fishermen. Solutions for combining sustainable uses of the same ocean space have thus seen increasing interest within the research community in Germany and in Europe over the past years. This paper was inspired by and presents the outcomes of a stakeholder analysis and in particular a stakeholder workshop. Central focus was placed on academics and private as well as public stakeholders engaged in current research efforts of combining offshore wind farms and aquaculture in the German North Sea. The paper identifies the overall acceptance of such a multi-use scenario in society, opportunities and constraints as perceived by the stakeholders, and key research gaps. The results confirm the assumption that there is a clear need, and also willingness on behalf of the policy makers and the research community, to find sustainable, resource- and space-efficient solutions for combined ocean use.

Description: While there is a great deal of global interest in the development of combined uses of open ocean installations, for commercial scale multi-use platforms for food and energy production and other potential applications, the transition from concept to reality has yet to come to fruition. While much is known about the economics, environmental, political and societal effects of individual production sectors, there are many unknowns and challenges with regard to economics, engineering, liability and social aspects of multi-use. Mutually agreed upon principles, such as those articulated in the Bremerhaven Declaration, and EU directives and grant funding opportunities to advance research and development indicate that progress, although measured, is being made. The development of true commercial-scale multi-use offshore platforms will require investment in demonstration projects and multi-national cooperation and collaboration across public and private sectors.

Description: Aquaculture of extractive species, such as bivalves and macroalgae, already supplies a large amount of the production consumed worldwide, and further production is steadily increasing. Moving aquaculture operations off the coast as well as combining various uses at one site, commonly called multi-use aquaculture, is still in its infancy. Various projects worldwide, pioneered in Germany and later accompanied by other European projects, such as in Belgium, The Netherlands, Norway, as well as other international projects in the Republic of Korea and the USA, to name a few, started to invest in robust technologies and to investigate in system design needed that species can be farmed to market size in high energy environments. There are a few running enterprises with extractive species offshore, however, multi-use scenarios as well as offshore IMTA concepts are still on project scale. This will change soon as the demand is dramatically increasing and space is limited.

Description: The increasing demand for ocean resources exerts an increasing pressure on the use of ocean space across all European Sea Basins. This underlines issues of compatibility (or conflicts) between different maritime uses as well as between economic activities and environmental protection. The idea of multi-use (MU), as a guiding concept for efficient allocation of compatible activities in the same marine space, can increase spatial efficiency and at the same time provide socio-economic and environmental benefits. However, its transition from a concept to real-world development is facing several barriers. Based on analysis of five European sea basins done under the Horizon 2020 MUSES project (Multi-Use in European Seas), this paper aims to clarify the concept of MU by discussing: 1) the definition in the literature and practice so far, and; 2) how existing regulatory and planning regimes are supporting and challenging the development of several MUs (considered as the most promising). The analytical methodology developed for the MUSES project relied on data collected via desk research and semi structured interviews with key stakeholders (e.g. industry, regulators), over the period of seven months. The semi-quantitative analysis of data conducted, identified the commonalities and differences among countries in respect to each of the analyzed MUs. The paper points out priorities for the MU development in different sea basins and recommends initial steps to overcome existing barriers, whilst maximizing local benefits. This paper is a starting point towards a broader scientific debate on: (i) what could be the role of management policies (like for instance maritime spatial planning - MSP) in supporting and fostering MU concept development, (ii) what are technical and technological challenges for technically advanced MUs, (iii) how added values of MUs concept (e.g. benefits for local economies, positive impacts on environment) could be enhanced.

Description: Aquaculture is projected to be a major supplier of marine proteins to large parts of the global population. This includes bivalves, which have a high potential to offset protein deficits, as they are highly adaptable to varying water temperature, salinity, desiccation, and oxygen conditions. This work is part of a two-piece contribution on novel marine aquaculture technology and details physical laboratory tests of a new cultivation system for bivalve farming called “Shellfish Tower”. The tested 1:20 model consists of a rectangular cage (2 × 2 m prototype scale) with a central buoyancy element and a height of 2 – 4 m. Testing was done in a current flume as well as a wave basin for current velocities between 0.4 – 2.2 m/s and wave heights of 1.6 to 5.0 m with periods between 5 to 14 s. The tests were conducted to prove the feasibility and functionality of this aquaculture system, which is usable for the collection and cultivation of mussel spat as well as for the grow-out of oysters, scallops, and seaweed in marine environments. Tests carried out in a current flume revealed that drag coefficients decrease with increasing current velocities, and range from Cd=0.5 to 2.5, while the mooring inclination increases from 12° to 84° with increasing flow velocity, which is highly dependant on the buoyancy related pretension. The examination of the mooring line tensions recorded in a wave basin showed that the largest values of snap-induced tension were up to 10 times that of the semi-static tension. The maximum-recorded tension on the system was 48 kN for a single and 89 kN for a double configuration, compared to non-snap tension values, which were in the range of 6 – 10 kN. The insights gathered in this study will inform the future design of aquaculture systems in high-energy environments and allow for an integration into numerical models.

Description: The purpose of this publication is to perform a system analysis of new cultivation technology for exposed bivalve farming. The technical feasibility of the new construction, called Shellfish Tower, was assessed. The device has gone through several very different phases of development on its way to the deployment of the prototype. These included multiple iterations during the designing stage, wave tank testing, fabrication, loading and unloading on trucks and vessels, deployment at sea, installation and assembly on the single mooring line, and bring it to its final position in a submerged mode 5m-10 m below the water surface. The final structure has a hexagonal body, with a centrally orientated variable buoyancy unit with culture sub-units on each of the six corners. These sub-units can be used for the culture of oysters (Magallana gigas – formally Crassostrea gigas) as well as for the collection of mussel spat (Perna canaliculus). Other possible candidates could be seaweed, lobsters, sponges or tunicates. The operational depth of the whole system can be at any depth but was tested at between 5 and 10 m below the water surface positioned on the mooring line between the screw anchor and surface floats for the prototype tests. The system was deployed in March 2019 six nautical miles off the Bay of Plenty, North Island (New Zealand), in exposed waters near a commercial mussel farm and has been in test mode since then. The modelled structure indicates a design tolerance of significant wave height of over 7 m and currents of over 0.8 m/s. Initial results show that the new design has survived waves at 4.6 m significant height and current velocities of up to 0.7 m•s-1, while showing best growth conditions of the cultured oysters as well as for the spat settlement of juvenile greenshell™ mussels.

Description: Drawing on a case study in Germany, this contribution explores the practical application of offshore aquaculture within offshore wind farms in view of the different stakeholders involved. Using a transdisciplinary research approach, an understanding of the rationalities and interests among the different involved stakeholder groups was explored. Offshore wind energy is high on the political agenda in Germany. The vast spatial requirements however inherit potential user conflicts with competing, and under current legislation excluded users such as fishermen. Solutions for combining sustainable uses of the same ocean space have thus seen increasing interest within the research community in Germany and in Europe over the past years. This paper was inspired by and presents the outcomes of a stakeholder analysis and in particular a stakeholder workshop. Central focus was placed on academics and private as well as public stakeholders engaged in current research efforts of combining offshore wind farms and aquaculture in the German North Sea. The paper identifies the overall acceptance of such a multi-use scenario in society, opportunities and constraints as perceived by the stakeholders, and key research gaps. The results confirm the assumption that there is a clear need, and also willingness on behalf of the policy makers and the research community, to find sustainable, resource- and space-efficient solutions for combined ocean use.

Description: The concept of co-location of marine areas receives an increased significance in the light of sustainable development in the already heavily used offshore marine realm. Within this study, different spatial co-location scenarios for the coupling of offshore aquacultures and wind farms are evaluated in order to support efficient and sustainable marine spatial management strategies. A Geographic Information System (GIS) and multi-criteria evaluation (MCE) techniques were combined to index suitable co-sites in the German exclusive economic zone of the North Sea. The MCE was based on criteria such as temperature, salinity or oxygen. In total, 13 possible aquaculture candidates (seaweed, bivalves, fish and crustaceans) were selected for the scenario configuration. The GIS modelling framework proved to be powerful in defining potential co-location sites. The aquaculture candidate oarweed (Laminaria digitata) revealed the highest suitability scores at 10–20 m depth from April to June, followed by haddock (Melanogrammus aeglefinus) at 20–30 m depth and dulse (Palmaria palmata) and Sea belt (Saccharina latissima) at 0–10 m depth between April and June. In summary, results showed several wind farms were de facto suitable sites for aquaculture since they exhibited high suitability scores for Integrated Multi-Trophic Aquaculture (IMTA) systems combining fish species, bivalves and seaweeds. The present results illustrate how synergies may be realised between competing needs of both offshore wind energy and offshore IMTA in the German EEZ of the North Sea. This might offer guidance to stakeholders and assist decision-makers in determining the most suitable sites for pilot projects using IMTA techniques.