Efforts to restore the native oyster Ostrea edulis and its associated habitats are gaining momentum across Europe. Several projects are currently running or being planned. To maximize the success of these, it is crucial to draw on existing knowledge and experience in order to design, plan and implement restoration activities in a sustainable and constructive approach. For the development of best practice recommendations and to promote multidimensional knowledge and technology exchange, the Native Oyster Restoration Alliance (NORA) was formed by partners from science, technology, nature conservation, consultancies, commercial producers and policy-makers. The NORA network will enhance scientific and practical progress in flat oyster restoration, such as in project planning and permitting, seed oyster production, disease management and monitoring. It also focuses on joint funding opportunities and the potential development of national and international regulatory frameworks. The main motivation behind NORA is to facilitate the restoration of native oyster habitat within its historic biogeographic range in the North Sea and other European seas along with the associated ecosystem services; services such as enhancing biodiversity, including enhanced fish stocks, nutrient cycling and sediment stabilization. NORA members agreed on a set of joint recommendations and strongly advise that any restoration measure should respect and apply these recommendations: The Berlin Oyster Recommendation is presented here. It will help guide the development of the field by developing and applying best practice accordingly. NORA also aims to combine the outreach activities of local projects for improved community support and awareness and to provide educational material to increase knowledge of the key ecological role of this species and increase awareness among regulators, permit providers and stakeholders. A synthesis of O. edulis restoration efforts in Europe is provided and underlines the general significance in the field.

Marine ecosystems of temperate regions are highly modified by human activity and far from their original natural status. The North Sea, known as an intensively used area, has lost its offshore oyster grounds due to overexploitation in a relatively short time. Native oyster beds as a once abundant and ecologically highly important biogenic reef-type have vanished from the North Sea ecosystem in most areas of both their former distribution and magnitude. Worldwide, oyster stocks have been severely exploited over the past centuries. According to estimates, about 85% of the worldwide oyster reef habitats have been destroyed over the course of the last century. This loss of oyster populations has meant far more than just the loss of a valuable food resource. Oyster reefs represent a characteristic benthic community which offers a variety of valuable ecosystem services: better water quality, local decrease of toxic algal blooms, increase in nutrient uptake, increase of bentho-pelagic coupling, increase in species richness, increase of multidimensional biogenic structures which provide habitat, food, and protection for numerous invertebrate and fish species. The aim of oyster restoration is to promote redevelopment of this valuable missing habitat. The development of strategies, methods, and procedures for a sustainable restoration of the European oyster Ostrea edulis in the German North Sea is currently a focus of marine nature conservation. Main drivers for restoring this ecological key species are the enhancement of biodiversity and ecosystem services in the marine environment. Results of these investigations will support the future development and implementation of a large-scale and long-term German native oyster restoration programme to re-establish a healthy population of this once-abundant species now absent from the region.

Aquaculture production plays an increasingly important role to meet the global demand for aquatic products and expands continuously. Most mariculture organisms are produced in coastal areas, where space is scarce and user conflicts exist. For extensive cultures farming off the coast at offshore sites could be a solution to eliminate these problems and facilitate further expansion of environmentally sustainable aquaculture. The aim of this study was to examine the biological adequacy of two candidate species for ostreiculture, the Pacific oyster Crassostrea gigas and the European flat oyster Ostrea edulis. Growth rates, condition and mortality in offshore environments were investigated by transferring oyster spat of both species to 4 different sites in 2004 and 2007. Samples were taken every six to eight weeks from April to October and length, width, height and dry mass were measured as well as the Condition Index (CI = dry mass meat •100/dry mass shell) was calculated. Results show that both oyster species grow successfully in a high-energy environment. Mean growth rates are similar to those measured in individuals from coastal habitats (wild banks and cultures) and the CI shows seasonal variation in both species. The survival rate for both species was N 99% in 2007. However, in the previous trial in 2004 a high mortality rate was observed for O. edulis at one single site at the end of the experiment. Differences were observed in the increase of shell length and dry mass between sites and size classes. Taking these results into account site-selection criteria for different offshore locations are presented. We conclude that offshore cultivation of oysters will be successful if site-selection criteria are examined carefully when choosing a location for offshore aquaculture.

Widespread global declines in shellfish reefs (ecosystem-forming bivalves such as oysters and mussels) have led to growing interest in their restoration and protection. With restoration projects now occurring on four continents and in at least seven countries, global restoration guidelines for these ecosystems have been developed based on experience over the past two decades. The following key elements of the guidelines are outlined: (a) the case for shellfish reef restoration and securing financial resources; (b) planning, feasibility, and goal setting; (c) biosecurity and permitting; (d) restoration in practice; (e) scaling up from pilot to larger scale restoration, (f) monitoring, (g) restoration beyond oyster reefs (specifically mussels), and (h) successful communication for shellfish reef restoration projects.

Offshore production of seafood is a promising approach to evade numerous specific problems related to aquaculture activities in coastal areas. The aim of this study was to investigate the biological performance of oysters, typical near-shore organisms and potent aquaculture candidates, in an offshore environment. Juveniles of two oyster species, Ostrea edulis and Crassostrea gigas, were transferred to an offshore cultivation site in the German North Sea and cultivated from April to October 2007. Samples were taken every six to eight weeks to determine biochemical and elemental compositions: total glycogen (TG), total protein, total lipid (TL) as well as lipid classes, fatty acids (FA) and the yields and ratios of carbon, hydrogen and nitrogen. Results show an increase in glycogen from spring to early summer for both species, which is related to high food abundance during spring phytoplankton bloom. During summer, glycogen storage revealed clear differences between O. edulis and C. gigas attributing to the reproductive activity of C. gigas but not O. edulis. TG contents ranged between 6% and 23% dry mass (DM) in O. edulis and between 5% and 16% DM in C. gigas. Total protein contents did not show significant seasonal variations and ranged between 34% and 41% DM in both species. TL contents increased during summer, although the increase was clearly more pronounced in C. gigas, followed by a decrease in both species in autumn. TL levels ranged between 7% and 14% DM in both species. Phospholipids and triacylglycerols were the main lipid classes in both oyster species, followed by sterols. FA compositions resembled those of near-shore-grown oysters. We conclude that offshorecultivated oysters exhibit a natural biological performance, emphasizing their suitability as offshore aquaculture candidates.

Bivalve habitat restoration is growing in geographic extent and scale globally. While addressing the wide‐scale loss of these biogenic habitats is still a key motivation behind restoration efforts, stakeholders and funders are increasingly drawn to shellfish restoration for the many ecosystem services these habitats provide. There is clear evidence for the provision of ecosystem services from species targeted for restoration in the USA, in particular Crassostrea virginica. Ecosystem services, however, remain largely unquantified or even undescribed for the majority of other species targeted for restoration. A structured review of the literature was undertaken and supplemented by expert knowledge to identify which ecosystem services are documented in the following other bivalve species targeted for restoration: Ostrea edulis, Ostrea angasi, Crassostrea rhizophorae, Perna canaliculus, Modiolus modiolus, Mytilus edulis, Mytilus platensis, Crassostrea gigas, Ostrea denselamellosa, Crassostrea ariakensis, and Crassostrea sikamea. Key knowledge gaps in quantifying ecosystem services and the ecosystem engineering properties of habitat‐building bivalves contributing to the provision of ecosystem services were identified. Ecosystem services with the potential to be widely applicable across bivalve habitat‐building species were identified. Though there is evidence that many of the ecosystem engineering properties that underpin the provision of ecosystem services are universal, the degree to which services are provided will vary between locations and species. Species‐specific, in situ, studies are needed in order to avoid the inappropriate transfer of the ecosystem service delivery between locations, and to further build support and understanding for these emerging targets of restoration.

a b s t r a c tThe 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 colocation 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 MultiTrophic 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.

According to the EU Marine Strategy Framework Directive (2008/56/EC), marine protected areas (MPA) should contribute to a good environmental status of the Europeans seas. Measures maintaining or restoring a favourable conservation status of protected species and habitats are mandatory according to the EU Habitats Directive (92/43/EEC). Identification of suitable sites for ecological restoration measures within MPAs is a crucial step towards successful conservation and sustainable MPA management. In terms of species restoration, it is important to restore the respective species with the best possible environment for growth, survival, fitness, and successful recruitment. This study provides a comprehensive list of site‐selection criteria for ecological species restoration. Three general categories were chosen: (1) ecological history: evidence for the historical distribution; (2) feasibility of restoration: regulating framework and logistics; and (3) environmental conditions: quality of abiotic and biotic factors. A total of 16 site‐selection criteria were identified and applied to biogenic reef restoration, namely for reefs of the native European oyster Ostrea edulis, in the German Bight. The Natura 2000 area Borkum Reef Ground was identified as a suitable site for oyster restoration. It is one of three MPAs in the German Exclusive Economic Zone of the North Sea, which have been declared as Nature Conservation Areas according to national legislation. The conservation objectives include maintenance or, if necessary, restoration of the habitat type ‘reefs’. As a reef‐building species, the European oyster O. edulis is of particular importance for this habitat type in terms of nature conservation. The step by step approach for site selection presented here is applicable for biogenic reef restoration elsewhere. The selected Natura 2000 area showcases the potential role and future perspective of European MPAs with regards to active conservation measures.