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The swimming performance of cultured finfish species is typically studied under steady flow conditions. However, flow conditions are mostly unsteady, for instance, as experienced in sea pens in exposed sea areas. Using a Loligo swim tunnel, we investigated the effects of swimming in steady and unsteady flows at increasing swimming speeds on post-smolt Atlantic salmon. Oxygen consumption (MO2), locomotory behaviour, and overall dynamic body acceleration (ODBA), as determined with implanted acoustic sensor tags, were compared between both flow conditions. Results were obtained for mean swimming speeds of 0.2 to 0.8 m.s−1 under both flow conditions. Sensor tags that were implanted in the abdominal cavity had no significant effects on MO2 and locomotory parameters. The MO2 of fish swimming in unsteady flows was significantly higher (15–53%) than when swimming in steady flows (p < 0.05). Significant interaction effects of ODBA with flow conditions and swimming speed were found. ODBA was strongly and positively correlated with swimming speed and MO2 in unsteady flow (R2 = 0.94 and R2 = 0.93, respectively) and in steady flow (R2 = 0.91 and R2 = 0.82, respectively). ODBA predicts MO2 well over the investigated range of swimming speeds in both flow conditions. In an unsteady flow condition, ODBA increased twice as fast with MO2 compared with steady flow conditions (p < 0.05). From these results, we can conclude that (1) swimming in unsteady flow is energetically more costly for post-smolt Atlantic salmon than swimming in steady flow, as indicated by higher MO2, and (2) ODBA can be used to estimate the oxygen consumption of post-smolt Atlantic salmon in unsteady flow in swim tunnels.

Marine aquaculture is playing an increasingly important role in the global food supply chain. Data from the Food and Agriculture Organization of the United Nations (FAO, 2020b) indicates that harvested fish account for at least 20% of the animal protein intake of 3.3 billion people, and global marine aquatic products are expected to grow by 155% from 2020 to 2050 according to the Marine Aquatic Forecast Report of DNV (2021). As the scale of mariculture grows in nearshore areas, severe environmental pollution and resource utilisation conflicts with competing users such as shipping, tourism, fishing and conservation are inevitable. Therefore, some companies or organisations, for example, Blue Economy Cooperative Research Centre in Australia, are considering moving the fish farms to offshore areas. Because of the lack of theoretical research and empirical practise, such as the determination of environmental loads and the mechanism of hydroelastic interactions between waves and flexible net structures, offshore fish farming still faces tremendous risks and challenges. This also means that cutting-edge science and technology in this field are gaining research traction from both academia and industry. At offshore sites, aquatic facilities exposed to high-energy environments will be subjected to more significant wave loads. Therefore, it is one of the core design considerations for engineers to effectively and accurately predict the hydroelastic behaviour of fish cages under the action of ocean waves. Based on this background, the present Ph.D. thesis will investigate the hydroelastic interaction between ocean waves and open-net fish cages. The specific objectives include: 1. Undertaking a systematic literature review to identify research trends and gaps in this field; 2. Establishing an innovative semi-analytical solution for the research question; 3. Simulating and analysing the hydroelastic behaviour of the net cage under wave action; 4. Conducting parametric studies on, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Eng & Built Env, Science, Environment, Engineering and Technology, Full Text

The University of Hawai‘i Aquaculture Program and the National Oceanic and Atmospheric Administration’s (NOAA) Hawaiian Islands Humpback Whale National Marine Sanctuary (sanctuary) co-hosted "Ho‘olālā i ka mahii‘a o kēia mua aku", a workshop focused on visioning the future of aquaculture in Hawai‘i. The workshop offered an opportunity to bring diverse stakeholders together to facilitate a dialogue on issues regarding aquaculture in Hawai‘i and to build relationships to promote future collaborations. Topics of discussion included food safety and security - sustaining local communities by enhancing locally produced and consumed foods; stimulating job creation while conserving natural and cultural resources, existing and future aquaculture projects, considerations for project siting and national aquaculture policies. A Workshop Advisory Team (WAT) was formed to plan the workshop and was comprised of cultural advisors, community and stakeholder representatives, and state and federal agency representatives. The WAT identified a workshop process, content, and potential participants. The workshop was the first of a series of planned discussions and brought together cultural and fishpond practitioners, community members, farmers, business and food industry representatives, subject matter experts, state and federal agency representatives and marine resource managers. The first day of the workshop was an information-sharing day open to the public. The format included presentations and panel discussions with opportunities for questions and answers. Presentations were provided on topics including: • Historical context of aquaculture in Hawai‘i • Current aquaculture activities in Hawai‘i • A national perspective of aquaculture • The role of the Department of Land and Natural Resources in the oversight of aquaculture in the State of Hawai‘i. Panel discussions included: Native Hawaiian aquaculture practices; today’s open ocean aquaculture; and cultural and environmental considerat

The warming of the Mediterranean Sea surface is currently estimated to have been 0.4°C per decade for the period 1985-2006, and the increase in water temperature may have negatively affected marine aquaculture, e.g. by decreasing productivity. Development of aquaculture without adequate planning can lead to unsustainable economic feasibility due to future climate stressors. In this sense, offshore mariculture could be an alternative for mitigating the effect of coastal warming. The purpose of this study was to evaluate the suitability of the coastline in terms of global warming and sea surface temperature trends in locations where fish aquaculture is currently being developed, as well as the spatial changes of thermal anomalies up to 30 km from the coast, during the last 31 yr in the western Mediterranean (Spanish coast). This study was conducted using EU Copernicus Marine Service Information, covering the period 1981-2018, with a spatial resolution of 4 × 4 km. The results show that, over the last decade, the Mediterranean coastal environment off the Iberian Peninsula has experienced an increase in temperature of around 1ºC due to global change, with a clear latitudinal pattern modified by mesoscale oceanographic processes. The development of offshore aquaculture at some latitudes mitigates the extreme aestival effects on surface water temperatures. Strategic plans for aquaculture development should be able to forecast and incorporate future climate projections and local oceanographic conditions, and offshore aquaculture may provide an alternative in some regions, depending on local oceanographic conditions.

Marine aquaculture is expanding offshore, where the environmental interactions are not yet fully understood. We performed a benthic environmental assessment of an offshore fish farm on unconsolidated sediment. The physicochemical variables showed marked changes just under the fish farm, although the structure of the community and its bioturbation potential were not influenced. Under no or minimum influence from the fish farm, the physicochemical variables, including acid-volatile sulphides and redox, were notably different to those found in unaffected coastal areas. For this reason, classifications of the environmental status based on physicochemical variables should be adapted to offshore areas. Despite the low degree of impact detected, the organic matter carrying capacity should be carefully determined to avoid environmental drawbacks in terms of fine-grained offshore sediments. Offshore aquaculture could have a lower environmental impact than other types of aquaculture located closer to the coast, but further research is needed to obtain conclusive results.

The warming of the Mediterranean Sea surface is currently estimated to have been 0.4°C per decade for the period 1985-2006, and the increase in water temperature may have negatively affected marine aquaculture, e.g. by decreasing productivity. Development of aquaculture without adequate planning can lead to unsustainable economic feasibility due to future climate stressors. In this sense, offshore mariculture could be an alternative for mitigating the effect of coastal warming. The purpose of this study was to evaluate the suitability of the coastline in terms of global warming and sea surface temperature trends in locations where fish aquaculture is currently being developed, as well as the spatial changes of thermal anomalies up to 30 km from the coast, during the last 31 yr in the western Mediterranean (Spanish coast). This study was conducted using EU Copernicus Marine Service Information, covering the period 1981-2018, with a spatial resolution of 4 × 4 km. The results show that, over the last decade, the Mediterranean coastal environment off the Iberian Peninsula has experienced an increase in temperature of around 1ºC due to global change, with a clear latitudinal pattern modified by mesoscale oceanographic processes. The development of offshore aquaculture at some latitudes mitigates the extreme aestival effects on surface water temperatures. Strategic plans for aquaculture development should be able to forecast and incorporate future climate projections and local oceanographic conditions, and offshore aquaculture may provide an alternative in some regions, depending on local oceanographic conditions.

Marine aquaculture is expanding offshore, where the environmental interactions are not yet fully understood. We performed a benthic environmental assessment of an offshore fish farm on unconsolidated sediment. The physicochemical variables showed marked changes just under the fish farm, although the structure of the community and its bioturbation potential were not influenced. Under no or minimum influence from the fish farm, the physicochemical variables, including acid-volatile sulphides and redox, were notably different to those found in unaffected coastal areas. For this reason, classifications of the environmental status based on physicochemical variables should be adapted to offshore areas. Despite the low degree of impact detected, the organic matter carrying capacity should be carefully determined to avoid environmental drawbacks in terms of fine-grained offshore sediments. Offshore aquaculture could have a lower environmental impact than other types of aquaculture located closer to the coast, but further research is needed to obtain conclusive results.

By moving away from coastal waters and hence reducing pressure on nearshore ecosystems, offshore aquaculture can be seen as a possible step towards the large-scale expansion of marine food production. Integrated multi-trophic aquaculture (IMTA) in nearshore water bodies has received increasing attention and could therefore play a role in the transfer of aquaculture operations to offshore areas. IMTA holds scope for multi-use of offshore areas and can bring environmental benefits from making use of waste products and transforming these into valuable co-products. Furthermore, they may act as alternative marine production systems and provide scope for alternative income options for coastal communities, e.g., by acting as nodes for farm operation and maintenance requirements. This paper summarizes the current state of knowledge on the implications of the exposed nature of offshore and open ocean sites on the biological, technological and socio-economic performance of IMTA. Of particular interest is improving knowledge about resource flows between integrated species in hydrodynamic challenging conditions that characterize offshore waters.

There has been a dramatic growth in seafood demand in recent years, leading to a development of offshore aquaculture. Offshore aquaculture is seen to possess various superiorities over traditional inland one; these include for example being away from contaminant sources, ensuring a healthy environment for fish and less harmful to the aquatic ecosystem. However, in order for an offshore fish cage to operate under violent conditions such as strong currents high waves and storms, its mechanical frame and mooring system must be able to sustain the mechanical load on it. It is therefore necessary to investigate the interaction between the current and the cage, typically the characteristics of and the factors affecting the flow over and through it. In this thesis, a numerical approach is employed; and the flow over and through a single cage and several cages arranged in different patterns is investigated in detail. The cage’s design is of a spherical and submersible type, however, here it is assumed to be totally submerged in the water. The spherical cage is modeled as a hollow sphere with its wall being a thin and porous layer, which represents the net and the mechanical frame. The porosity of this layer is estimated based on practical design of this type. Other characteristic parameters of the porous medium are determined by fitting with results of the flow field available in the literature. For the purpose of verification of the numerical approach, simulation of a flow over a solid sphere is conducted. It is noted that when the porosity approaches zero, a situation when complete bio-fouling happens, the cage resembles the solid sphere. Special focus is on the flow inside the cage/cages, where the low is observed to weaken, reducing the exchange of well-oxygenated water and nutrients. Effect of the bio-fouling phenomena is also investigated by associating them with a porosity; drag force acting on the cage is computed accordingly. Moreover, it is found that there exists

Aquaculture production is projected to expand from land-based operations to the open ocean as demand for seafood grows and competition increases for inputs to land-based aquaculture, such as freshwater and suitable land. In contrast to land-based production, open-ocean aquaculture is constrained by oceanographic factors, such as current speeds and seawater temperature, which are dynamic in time and space, and cannot easily be controlled. As such, the potential for offshore aquaculture to increase seafood production is tied to the physical state of the oceans. We employ a novel spatial model to estimate the potential of open-ocean finfish aquaculture globally, given physical, biological and technological constraints. Finfish growth potential for three common aquaculture species representing different thermal guilds-Atlantic salmon (Salmo salar), gilthead seabream (Sparus aurata) and cobia (Rachycentron canadum)-is compared across species and regions and with climate change, based on outputs of a high-resolution global climate model. Globally, there are ample areas that are physically suitable for fish growth and potential expansion of the nascent aquaculture industry. The effects of climate change are heterogeneous across species and regions, but areas with existing aquaculture industries are likely to see increases in growth rates. In areas where climate change results in reduced growth rates, adaptation measures, such as selective breeding, can probably offset potential production losses.

A biometric, nutritional and sensory analysis of raw and cooked mussels comparing Mytilus sp. from the north-west coast of Portugal and Spain (Minho and Galicia, respectively) and the new offshore production site of Armona (Algarve, south Portugal) was carried out. In addition, multiple factorial analysis was performed to explore potential relationships between sensory attributes and nutritional content properties between the different mussels. Results showed that, at similar times of sale, biometrics of mussels from Armona and Vigo were similar and bigger than the remaining. Nonetheless, despite some similarities in proximate composition, mussels presented differences in lipid classes, fatty acid content and free amino acids profiles. These differences were not fully reflected in the sensory assessment by the panel, which were able to distinguish different production sites in raw specimens but displayed problems in discrimination these in cooked mussels. Some nutritional components were related to specific sensory sensations.

Globally, humans are harvesting the majority of capture fisheries at or above maximum sustainable yield, yet the demand for seafood is ever growing, a trend that cannot be met by the apparent plateau or possible decline of capture fisheries. Aquaculture appears to be an essential part of the solution, although it has become an increasingly controversial form of food production due to human health concerns and negative environmental impacts, as it has developed into a viable industry over the past 20 years. The US Department of Commerce is currently drafting legislation for the purpose of creating a streamlined permitting process for offshore aquaculture facilities in the US exclusive economic zone (EEZ). The objective of the legislation, referred to as the National Offshore Aquaculture Act of 2005, is to increase current US aquaculture production from a $1 billion per year industry to $5 billion annually by the year 2025. However, permitting aquaculture facilities in federal waters may have negative impacts on marine biodiversity in regards to increased disease transmission to wild stocks, pollution, escaped exotic or genetically modified species, as well as interference with natural marine mammal behavior and protected species. The purpose of this review is to evaluate the sustainability and feasibility of the US plan to intensity aquaculture efforts in the US EEZ through current case studies and interviews of industry experts and scientists, and to produce recommendations for a future policy framework based on the impacts to marine biodiversity. Given the many uncertainties, the Department of Commerce should consider the following limits to offshore aquaculture projects: 1) No aquaculture activities producing non-native species should be permitted in federal waters to protect wild species that may be at risk of hybridizing or losing habitat to nonendemic escapees; 2) A moratorium on genetically modified species should remain until their safety can be proven in lan

Globally, humans are harvesting the majority of capture fisheries at or above maximum sustainable yield, yet the demand for seafood is ever growing, a trend that cannot be met by the apparent plateau or possible decline of capture fisheries. Aquaculture appears to be an essential part of the solution, although it has become an increasingly controversial form of food production due to human health concerns and negative environmental impacts, as it has developed into a viable industry over the past 20 years. The US Department of Commerce is currently drafting legislation for the purpose of creating a streamlined permitting process for offshore aquaculture facilities in the US exclusive economic zone (EEZ). The objective of the legislation, referred to as the National Offshore Aquaculture Act of 2005, is to increase current US aquaculture production from a $1 billion per year industry to $5 billion annually by the year 2025. However, permitting aquaculture facilities in federal waters may have negative impacts on marine biodiversity in regards to increased disease transmission to wild stocks, pollution, escaped exotic or genetically modified species, as well as interference with natural marine mammal behavior and protected species. The purpose of this review is to evaluate the sustainability and feasibility of the US plan to intensity aquaculture efforts in the US EEZ through current case studies and interviews of industry experts and scientists, and to produce recommendations for a future policy framework based on the impacts to marine biodiversity. Given the many uncertainties, the Department of Commerce should consider the following limits to offshore aquaculture projects: 1) No aquaculture activities producing non-native species should be permitted in federal waters to protect wild species that may be at risk of hybridizing or losing habitat to nonendemic escapees; 2) A moratorium on genetically modified species should remain until their safety can be proven in lan