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This work attempts to define metrics for hydrodynamic exposure, using known oceanographic variables to provide a universal site assessment method for mariculture structures. Understanding environmental conditions driving open-ocean mariculture siting is crucial in establishing consistent ocean governance, minimizing adverse environmental impacts, and facilitating economically sustainable farm operations. To provide a metric of oceanic conditions and associated requirements for structural design and operation of aquaculture systems, six Exposure Indices (EI) are proposed that consider physical energy levels related to hydrodynamic forces at a site. Four of the proposed indices consider only environmental conditions, while the other two also consider the dimensions of the gear that is exposed to the external loads. These indices are: Exposure Velocity (EV), Exposure Velocity at Reference Depth (EVRD), Specific Exposure Energy (SEE), Depth-integrated Energy Flux (DEF), Structure-centered Depth-integrated Energy (SDE), and a Structure-centered Drag-to-Buoyancy Ratio (SDBR). While these indices are derived with a focus on aquaculture structures, they may also have applications for estimating biological stressors and operational challenges. The proposed exposure indices were evaluated for a range of known aquaculture sites around the world. A sensitivity analysis was conducted that quantified the relationship between the exposure indices and storm event return period. At a regional scale, hindcast numerical data for the German Bight combined with calculations of 50-year extreme values were used to calculate and map each proposed index spatially. Resulting maps showed that exposure is not simply a function of distance from shore. The six indices show plausible performance regarding the objective assessment of aquaculture sites. The authors herein present the indices to the aquaculture and ocean engineering communities for discussion, application, and potential adoption of one or more of the proposed indices. [ABSTRACT FROM AUTHOR]

The term "offshore" with regards to aquaculture has hitherto encompassed various perspectives, including technology, geographic location, legal jurisdiction, and more. To resolve the ambiguity in this term and understand its implications for current and future aquaculture development, "offshore" should be resolved into two separate metrics: distance from shore and energy exposure. The United Nations Convention on the Law of the Sea (UNCLOS) distinguishes between internal waters, territorial sea, contiguous zone, exclusive economic zone (EEZ), and the high seas, but currently has no precise definition for "offshore" in its provisions, and therefore no applicable laws pertaining to "offshore" aquaculture. Regulating a multi-technology aquaculture sector may require integrating new spatial concepts into the law rather than merely adapting and extending current regulatory designs to include new production concepts. The metrics of distance from shore and exposure are seen as a range rather than a specific threshold, allowing for a continuum. Distance from shore is readily quantified as a distance from a baseline. To rigorously quantify the exposure, the influence and interactions of oceanic parameters (water depth, water current, and wave height and period) we utilized to generate six indices. These oceanic parameters are seen as the main contributions which influence the physical and some biological parameters required for site, species, and technology selection. Four shellfish, three seaweed, and three finfish sites along with 20 potential aquaculture sites were examined using the indices in association with the energy index to determine tolerances of the structures and their ability to cultivate their relevant species. Two indices, Specific Exposure Energy (SEE) and Exposure Velocity (EV), were selected for utilization in the analysis of sites based on their ease of use and applicability. The interaction between the energy indices and various aspects of farm operations and performance were explored. The indices developed and used in the case studies presented have been shown to be useful tools in the general assessment of the energy that will influence the species and equipment selection at potential aquaculture sites. The indices do not provide a definitive answer as to the potential financial success of a site as this requires other inputs relating to infrastructure costs, annual production, distance from port, sales strategy, etc. However, the Specific Exposure Energy index creates a useful tool to describe site energy and be comprehensible to a wide range of stakeholders. We recommend the SEE index be adopted as the predominant tool to communicate the exposure level of aquaculture sites. [ABSTRACT FROM AUTHOR]

Aquaculture in exposed and/or distant ocean sites is an emerging industry and field of study that addresses the need to improve food security along with the challenges posed by expansion of urban and coastal stakeholders into nearshore and sheltered marine waters. This move necessitates innovative solutions for this industry to thrive in high-energy environments. Some innovative research has increased understanding of the physics, hydrodynamics, and structural requirements enabling the development of appropriate systems. The blue mussel (Mytilus edulis), the New Zealand green shell or green lipped mussel (Perna canaliculus), and the Pacific Oyster (Magallana gigas), are the primary targets for commercial exposed bivalve aquaculture. Researchers and industry members are actively advancing existing structures and developing new structures and methodologies for these and alternative high-value species suitable for such conditions. For macroalgae (seaweed) cultivation, such as sugar kelp (Saccharina latissimi), oar weed (Laminaria digitata), or kelp sp. (Ecklonia sp.), longline systems are commonly used, but further development is needed to withstand fully exposed environments and improve productivity and efficiency. In marine finfish aquaculture, three primary design categories for open ocean net pens are identified: flexible gravity pens, rigid megastructures, closed pens, and submersible pens. As aquaculture ventures into more demanding environments, a concerted focus on operational efficiency is imperative. This publication considers the commercial and research progress relating to the requirements of aquaculture's expansion into exposed seas, with a particular focus on the cultivation of bivalves, macroalgae, and marine finfish cultivation technologies and structural developments. [ABSTRACT FROM AUTHOR]

This work attempts to define metrics for hydrodynamic exposure, using known oceanographic variables to provide a universal site assessment method for mariculture structures. Understanding environmental conditions driving openocean mariculture siting is crucial in establishing consistent ocean governance, minimizing adverse environmental impacts, and facilitating economically sustainable farm operations. To provide a metric of oceanic conditions and associated requirements for structural design and operation of aquaculture systems, six Exposure Indices (EI) are proposed that consider physical energy levels related to hydrodynamic forces at a site. Four of the proposed indices consider only environmental conditions, while the other two also consider the dimensions of the gear that is exposed to the external loads. These indices are: Exposure Velocity (EV), Exposure Velocity at ReferenceDepth (EVRD), SpecificExposureEnergy (SEE), Depth integrated Energy Flux (DEF), Structure-centeredDepth-integrated Energy (SDE), and aStructure-centeredDrag-to-BuoyancyRatio (SDBR). While these indices are derived with a focus on aquaculture structures, they may also have applications for estimating biological stressors and operational challenges. The proposed exposure indiceswere evaluated for a range of known aquaculture sites around the world. A sensitivity analysis was conducted that quantified the relationship between the exposure indices and storm event return period. At a regional scale, hindcast numerical data for the German Bight combined with calculations of 50-year extreme values were used to calculate and map each proposed index spatially. Resulting maps showed that exposure is not simply a function of distance from shore. The six indices show plausible performance regarding the objective assessment of aquaculture sites. The authors herein present the indices to the aquaculture and ocean engineering communities for discussion, application, and potential adoption of one or more of the proposed indices. [ABSTRACT FROM AUTHOR]

When moving from a very sheltered aquaculture site to a very exposed oceanic aquaculture site, the energy increases proportionally in a continuum. Lojek et al. (in review) considered the primary influential parameters (water current, wave height, wave period, wavelength and water depth) which influence the species, structure, technology, methods, and operational aspects of any aquaculture endeavour and investigated six possible indices which cover these variables. Added to advanced computer modelling, assisted by detailed and constant environmental monitoring, it may be possible to refine site selection, structure selection and design, species selection, equipment and logistic requirements and health and safety requirements. This manuscript has selected two indicative indices: Specific Exposure Energy (SEE) index and Exposure Velocity (EV) index from the potential equations provided by Lojek et al. (in review) and compared them with known operational aquaculture sites highlighting present structural capability and limitations. The two indices are also utilized to reflect on their suitability for assessing sample sites with respect to biological, technological, operational or maintenance aspects of aquaculture activities. The indices have shown themselves to be useful tools in the general assessment of the energy that will influence the species and structure selection at potential aquaculture sites. This information can help prospective fish farmers characterize their sites concisely and accurately to consultants, regulators, equipment vendors, and insurance brokers. [ABSTRACT FROM AUTHOR]

The terms "offshore" and "open ocean" have been used to describe aquaculture sites that are further from the coast or in higher energy environments. Neither term has been clearly defined in the scientific literature nor in a legal context, and the terms are often used interchangeably. These and other related terms (for example "exposed", "high-energy") variously refer to aspects of a site such as the geographic distance from shore or infrastructure, the level of exposure to large waves and strong currents, the geographic fetch, the water depth, or some combination of these parameters. The ICES Working Group (ICES, 2024) on Open Ocean Aquaculture (WGOOA) therefore identified a need to define the terminology to reduce ambiguity for these types of aquaculture sites or more precisely, to: (1) promote a common understanding and avoid misuse for different classifications; (2) enable regulators to identify the characteristics of a marine site; (3) allow farmers to be able to assess or quantitatively compare sites for development; (4) equip developers and producers to identify operational parameters in which the equipment and vessels will need to operate; (5) provide insurers and investors with the terminology to consistently assess risk and premiums; and (6) circumvent the emergence of narratives that root in different cognitive interpretations of the terminology in public discourse. This paper describes the evolution of the use of the term "offshore aquaculture" and define the most relevant parameters to shift to a more definitive and robust term "exposed aquaculture" that can inherently relay clearer information. Adoption of this more definitive definition of "exposed" will allow the user to define a site with more than just distance from shore. Key differences and the importance of these terms are discussed that affect various interest groups. Follow-up articles in this compilation from scientific members of the WGOOA as well as other scientists outside ICES are incorporated that develop a set of definitions and a rigorous exposure index. [ABSTRACT FROM AUTHOR]