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: 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: The purpose of this study was to investigate whether meat from blue mussels (Mytilus edulis) harvested from offshore structures could be used as an alternative protein source in aquaculture fish feed for turbot (Scophthalmus maximus). Two feeding experiments with turbot were conducted in an initial experiment to test the applicability of mussel meal as a fishmeal replacement and/or supplement in turbot feed. In experiment A, the welfare, acceptance, and digestibility of feedstuff with 100%, 50% and 0% of mussel meal replacement for the fishmeal were tested for 8 weeks. In experiment B that followed, the convenience ratio of mussel meal protein in turbot feed for optimum growth was examined. Feedstuff with 25%, 10% and 0% of mussel meal were also fed for 8 (+6) weeks. Growth rates of fish were measured every 2 weeks and their health condition (liver somatic index) determined at the beginning and end of the experiments. Experiment A revealed that a replacement of fishmeal with either 100% or 50% mussel meal resulted in depressed growth (SGR: 1.31 ± 0.04 with 100% mussel meal; 1.54 ± 0.04 with 50% mussel meal; 1.71 ± 0.07 with 0% mussel meal). Experiment B revealed that a fishmeal replacement with 10% or 25% of mussel meal did not reduce growth nor did it have a negative effect on the health of the tested turbot. The study revealed that mussel meal has a high potential to serve as a supplement or as a fishmeal replacement in feed for turbot raised in aquaculture systems. Thus, its use in commercial aquaculture should be given future consideration.

Description: The investigation and application of a wide range of dietary supplements, such as probiotics, prebiotic and other additives, are increasingly popular in aquaculture research and practice. To date few studies have attempted to quantify the value of commercially available additives in improving growth performance of juvenile turbot (Scophthalmus maximus) and in compensating potential growth reduction resulting from high levels of plant protein (PP) in carnivorous fish diets. Two experiments were conducted to investigate the effect of different active ingredients in diet additives on turbot. I) Five diets supplemented with (1) yeast b-glucan and mannan oligosaccharides (GM), (2) alginic acid from brown algal extracts (AC), (3) yeast nucleotides and RNA (NR), (4) potassium diformate (PDF) and (5) bacteria strains Bacillus subtilis and B. licheniformis (BS), containing fish meal (FM) as the only protein source, were fed to turbots (initial weight 48.8 g ± 5.2 g) over 112 days. II) Four diets supplemented with (1) GM, (2) AC, (3) NR and (4) BS, containing soy protein concentrate (SPC) and wheat gluten (WG) as a partial replacement of FM, were fed to turbots (initial weight 95.8 g ± 17.7 g) over 84 days. A non-supplemented FM diet (exp. I) and an FM- and PP-based diet (exp. II), respectively, were used as control diets. Diet additives did not promote additional weight gain, specific growth rate (SGR), daily feed intake (DFI) and feed conversion ratio (FCR) in turbot fed FM- or PP-based diets (p 〉 0.05) when compared to isocaloric control diets in both experiments. Growth of turbots fed the high FM content control diet (II) was significantly higher than all other treatments (p 〈 0.01). Body proximate composition, condition factor (K) and liver index (HSI) remained unaffected by additive supplementation in fish fed either FM or PP diets (p 〉 0.05). Results indicate that reported benefits for specific diet additives cannot be assumed to function or applied across species boundaries and age classes. In addition, dietary additive application may not be economically valid for larger animals and/or animals not exposed to specific culture-related stressors. The benefits of popular additives to high value species such as S. maximus remains to be tested under specific immune or physical stress situations and at crucial larval and early juvenile stages.

Description: Technological solutions to increase the efficiency of spatial use can play a key role as part of the toolbox of marine spatial planning. Co-locating of multiple ocean uses can potentially increase the production and enjoyment of the ocean while limiting impacts. However, a basic precondition for co-locating or coproduction is that all parties' private incentives are aligned. We use a case study of co-locating an offshore wind energy firm and a mussel aquaculture firm to assess the incentive structure for cooperation and to demonstrate that social benefits from co-locating exist. We find that there is room for cooperation between firms based on potential cost sharing and that the demonstrated social benefits may arise without government intervention.

Description: The purpose of this study was to investigate the effectiveness of 11 different culture media for production of the free-living nematode Turbatrix aceti. Several other harvesting methods were tested in addition to mass production. A further focus was the investigation of amino acid alterations caused by the application of various media during the culture of T. aceti and two additional nematode species, Panagrellus redivivus and Caenorhabditis elegans. Finally, a cost analysis for the production of T. aceti was generated and its outcome compared to the production of conventional live feed organisms. Altogether 11 liquid culture media were tested for mass production of the nematode Turbatrix aceti using a minimum of effort in terms of labour and costs. Six harvesting methods, including filtration as well as active swimming of T. aceti were evaluated. Additional to the culture of T. aceti in four of the above-mentioned media, the nematodes P. redivivus and C. elegans were cultured on two different solid media. Cost analysis for the production of T. aceti includes those of the media, the equipment, as well as the labour costs for culture and harvest. An average density of approx. 30 × 106 ± 8.13 × 106 nematodes L−1 was achieved for T. aceti. The most efficient method (20 μm filtration) allowed harvesting 85.3 ± 2.7% of the nematodes from the medium without disturbing the particles. Lowest efficiency was achieved by combining sedimentation and filtration, accomplishing a harvest of 42.1 ± 5.8%. The amino acid profile of all three nematode species turned out to be both stable and very similar. Amino acid enrichment had little effect. The costs for producing one million T. aceti individuals ranged between 5.39 and 6.19 €, where labour costs accounted for 73 to 84% of the total production costs. In conclusion, T. aceti appears to be very robust, easy to handle, as well as cheaper to cultivate compared to other live-feed organisms. Therefore, its use in commercial aquaculture should be given future consideration.

Description: By incorporating the free-swimming nematode Turbatrix aceti into early feeding regimes of the European whitefish Coregonus maraena, the suitability of this nematode species was investigated as an alternative to Artemia nauplii. During a 14-day feeding trial in a total of 25 aquaria each 1.7 L (each treatment n = 5, 255 larvae/tank) T. aceti was used either as the sole live food or in combination with Artemia nauplii or microdiet to determine the effect of T. aceti on growth performance and survival rate of C. maraena. By analysing the fatty acid composition of T. aceti prior to and after enrichment with INVE spresso® it was investigated whether the amount of n3-polyunsaturated fatty acids (n3-PUFA) in T. aceti could be further enhanced. Supplementation of Artemia nauplii with T. aceti increased growth significantly within the first 5 days of rearing in comparison to the non-supplemented food treatments (14.39 ± 0.15 mm compared to 13.44 ± 0.18 mm; mean ± SE). However, growth and survival of juvenile C. maraena on nematode-supplemented Artemia nauplii did not differ significantly from non-supplemented Artemia nauplii at the end of the 14-day rearing period (15.22 ± 0.15 mm compared to 14.86 ± 0.24 mm). All feeding treatments containing Artemia nauplii showed significantly higher growth and lower mortality at the end of the experiment in comparison to diets containing only the microdiet or T. aceti or a combination thereof. The overall low performance of T. aceti alone can most likely be explained by an insufficient capacity of C. maraena to digest this nematode species efficiently. Enrichment with INVE spresso® successfully increased the proportion of DHA in the T. aceti tissue. The results reveal that T. aceti cannot be considered a full alternative to Artemia nauplii, at least not in the rearing of C. maraena, but might be a useful vector of essential fatty acids within the early rearing period of this and potentially other fish species when provided as live food along with Artemia nauplii.