Description: Worldwide the renewable energy sector is expanding at sea to address increasing demands. Recently the race for space in heavily used areas such as the North Sea triggered the proposal of co-locating other activities such as aquaculture or fisheries with passive gears in offshore wind farms (OWFs). Our interdisciplinary approach combined a quantification of spatial overlap of activities by using Vessel Monitoring System and logbook data with a stakeholder consultation to conclude and verify on the actual feasibility of co-location. In the German Exclusive Economic Zone (EEZ) of the North Sea up to 90% of Danish and 40% of German annual gillnet fleet landings of plaice overlapped with areas where OWFs are developed. Our results indicated further that the international gillnet fishery could lose up to 50% in landings within the North Sea German EEZ when OWF areas are closed entirely for fisheries. No spatial overlap was found for UK potters targeting brown crab in the German EEZ. We further identified a number of key issues and obstacles that to date hinder an actual implementation of co-location as a measure in the marine spatial planning process: defining the legal base; implementation of safety regulations; delineation of minimum requirements for fishing vessels such as capacities, quotas, technical equipment; implementation of a licensing process; and scoping for financial subsidies to set up business. The stakeholder consultation verified the scientific findings and highlighted that all those points need to be addressed in a planning process. In the German EEZ we have shown that the socio-economic importance of spatial overlap varies within planning boundaries. Therefore we recommend an interdisciplinary bottom-up approach when scoping for suitable areas of co-location. Hence, an informed marine spatial planning process requires comprehensive and spatial explicit socio-economic viability studies factoring in also ecological effects of OWFs on target species.

Description: Offshore wind power generation requires large areas of sea to accommodate its activities, with increasing claims for exclusive access. As a result, pressure is placed on other established maritime uses, such as commercial fisheries. The latter sector has often been taking a back seat in the thrust to move energy production offshore, thus leading to disagreements and conflicts among the different stakeholder groups. In recognition of the latter, there has been a growing international interest in exploring the combination of multiple maritime activities in the same area (multi-use; MU), including the re-instatement of fishing activities within, or in close proximity to, offshore wind farms (OWFs). We summarise local stakeholder perspectives from two sub-national case studies (East coast of Scotland and Germany's North Sea EEZ) to scope the feasibility of combining multiple uses of the sea, such as offshore wind farms and commercial fisheries. We combined a desk-based review with 15 semi-structured qualitative interviews with key knowledge holders from both industries, regulators, and academia to aggregate key results. Drivers, barriers and resulting effects (positive and negative) for potential multi-use of fisheries and OWFs are listed and ranked (57 factors in total). Factors are of economic, social, policy, legal, and technical nature. To date, in both case study areas, the offshore wind industry has shown little interest in multi-use solutions, unless clear added value is demonstrated and no risks to their operations are involved. In contrast, the commercial fishing sector is proactive towards multi-use projects and acts as a driving force for MU developments. We provide a range of management recommendations, based on stakeholder input, to support progress towards robust decision making in relation to multi-use solutions, including required policy and regulatory framework improvements, good practice guidance, empirical studies, capacity building of stakeholders and improvements of the consultation process. Our findings represent a comprehensive depiction of the current state and key stakeholder aspirations for multi-use solutions combining fisheries and OWFs. We believe that the pathways towards robust decision making in relation to multi-use solutions suggested here are transferable to other international locations.

Description: SummaryThe aim of this study was to identify scientific criteria and to acquire performance data for the development of mariculture in the context of sustainable multifunctional use of offshore space and natural resources.In connection with current plans for a massive expansion of wind farms in offshore areas of the North Sea, the idea emerged to combine these with the installation of extensive mariculture for bivalves and macroalgae. Since offshore wind farms provide safety from shipping and infrastructure for attachment and service support, the opportunity for a multiple-use concept presented itself. However, prior to such a multifunctional development, it is necessary to determine the appropriate biological, technological and management requirements as well as the performance characteristics that would allow the employment of favourable and cost-effective methodologies. To this end, spezial focus was placed on the combination of extensive offshore shellfish and seaweed farming at exposed sites within the proposed offshore wind farms.This thesis deals in detail with1. the effects of abiotic and biotic factors on the growth potential of indigenous macroalgae and bivalves in extensive mariculture systems exposed to the stressful conditions of offshore habitats: (a) effects of physical forces on the cultivated species, (b) various parameters characterising the growth performance of species, (c) testing these parameters while using a variety of substrates and technical setups, (d) survival and health conditions, (e) recruitment, (f) parasite infestation of mussels in relation to inshore and offshore exposure, and (g) site-specific responses of the species to the various harsh offshore environments,2. the interaction between physical offshore processes and man-made structures in areas of the German North Sea Territory where mariculture has potential,3. the conditions for possible combination of mariculture systems with offshore wind farms in terms of the legal framework and possible management strategies, and4. the socio-economic and legal consequences and interactions for offshore mussel farming with the existing conventional inshore bottom culture activities.The research locations were specifically selected sites in the offshore region of the German Bight, mainly in the outer estuary of the River Weser, the offshore waters off the Island of Helgoland, several offshore areas where wind farms are planned, and habitats along the northern part of the Island of Sylt.In this yet relatively young research field the performance of different offshore culture systems with attached macroalgae (Laminaria saccharina) and blue mussels (Mytilus edulis) was assessed at monthly sampling intervals. These procedures were carried out using research vessels, boats and scuba surveys, while determining morphometric parameters (e.g. length, width, thickness) as well as weight for growth analysis of mussels and seaweeds. Furthermore, the condition index, the meat content and the degree of parasite infestation of blue mussels were determined. The abundance of mussel larvae in the water column and the resulting settlement success of post-larvae on various spat collectors were investigated. Seaweed studies included attachment strength, breaking and drag forces on kelp sporophytes in order to describe the resistance of cultivated Laminarians to high energy environments. Additional assessment criteria were biochemical parameters (e.g. chlorophyll-, nutrient-, POC- and TON-concentrations and their ratios) to describe the food availability for mussels and the nutrient composition for algal growth as well as oceanographic parameters (currents, waves, swell, salinity, temperature, light attenuation) to describe the wave climate and current velocities of the study sites in the offshore environment. Technical studies comprised two system designs (longline, ring structure) of various set ups (submerged or floating mode) in different locations (offshore or inshore) to find an appropriate culture design to sustain growth and survival of cultivated species. Further, a specially designed offshore spat collector was used for settlement investigations of mussel post larvae. Some fundamental studies were carried out in order to pave the way for the realisation of open ocean aquaculture in offshore wind farms (e.g. multifunctional use of offshore habitats in terms of avoidance of stakeholder conflicts, the legal framework for such activities in coastal areas and in the Exclusive Economic Zone (EEZ), the multi-use concept in terms of integrated coastal zone management).Laminaria saccharina showed sufficient length increments in offshore habitats growing on a submerged ring system. It could be demonstrated by drag and breaking-/dislodgement force experiments that algae were capable of resisting the high-energy environment of the North Sea. The concentration of mussel larvae in the water column decreased offshore and resulted in a low settlement success while at the same time infestation load decreased and was lacking at offshore suspended collectors. The three system designs showed different results. While the offshore ring proved to be superior for seaweed cultivation under the harsh conditions, the longline showed some major drawbacks in terms of materials used, design and installation modes (submerged or floating). The spat collector largely withstood the harsh hydrodynamic conditions of the North Sea. The hitherto fragmented legal framework for the offshore waters was found to be one of the key constraints for the successful implementation of multifunctional use schemes. However, participation of all involved stakeholders may provide a window of opportunity to turn the existing lack of offshore regulations into a positive momentum, as scope exists to move with the development of new offshore co-management concepts beyond existing management approaches.Whether such offshore installations would provide sufficient economic returns could not be answered yet, as experience on the maintenance of offshore wind farms is lacking so far.However, the discovery that Laminaria saccharina resists offshore forces and shows sufficient length increments and mussels growing in offshore habitats are not affected by parasites may provide a key incentive for positive commercial use.It thus can be shown that there is a high potential for farming the deep blue in the German EEZ, provided that some of the constraints, of which the lack of legal framework and technical aspects seems to be most severe, are resolved in the near future.