7This study investigated the potential use of two "species distribution models" (SDMs), 8Mahalanobis Typicality and Maxent, for aquaculture site selection. SDMs are used in 9 ecological studies to predict the spatial distribution of species based on analysis of 10 conditions at locations of known presence or absence. Here the input points are aquaculture 11 sites, rather than species occurence, thus the models evaluate the parameters at the sites 12 and identify similar areas across the rest of the study area. This is a novel approach that 13 avoids the need for data reclassification and weighting which can be a source of conflict and 14 uncertainty within the commonly used multi-criteria evaluation (MCE) technique. Using 15 pangasius culture in the Mekong Delta, Vietnam, as a case study, Mahalanobis Typicality 16 and Maxent SDMs were evaluated against two models developed using the MCE approach. 17Mahalanobis Typicality and Maxent assess suitability based on similarity to existing farms, 18 while the MCE approach assesses suitability using optimal values for culture. Mahalanobis 19 Typicality considers the variables to have equal importance whereas Maxent analyses the 20 variables to determine those which influence the distribution of the input data. All of the 21 models indicate there are suitable areas for culture along the two main channels of the 22 Mekong River which are currently used to farm pangasius and also inland in the north and 23 east of the study area. The results show the Mahalanobis Typicality model had more high 24 scoring areas and greater overall similarity than Maxent to the MCE outputs, suggesting, for 25 this case study, it was the most appropriate SDM for aquaculture site selection. With suitable 26 input data, a combined SDM and MCE model would overcome limitations of the individual 27 approaches, allowing more robust planning and management decisions for aquaculture, 28 other stakeholders and the environment. 29 30

The tilapia fishery in a large Mexican reservoir has declined in recent years, promoting efforts to enhance stock quality in conjunction with feasibility studies for cage aquaculture. Spatial models to optimize cage location have been developed, incorporating aspects of topography, climate, hydrography, water quality and quantity, land use, infrastructure and socioeconomics. Three cage sizes were modelled, 5, 10 and 15 m diameter, for both high- and low-water levels. When full the, reservoir has a total area of 312 km2 but a reduction in water level of 13 m was recorded between wet and dry seasons, significantly reducing the surface area available for cages to 265 km2. The results indicate a significant difference in the availability of sites between seasons. For the small, medium and large cages at high water level, the areas classified as highly suitable or suitable were 151, 184 and 146 km2, respectively, while at low-water level these areas reduced to 113, 88 and 62 km2. Modelling this change in water level and the subsequent loss of available sites provide qualitative and quantitative guidelines for the development of aquaculture sites, their seasonal management and future monitoring, outcomes that can only be achieved using Geographical Information Systems and associated technologies

Offshore aquaculture has gained momentum in recent years, and the production of an increasing number of marine fish species is being relocated offshore. Initially, predictions of the advantages that offshore aquaculture would present over nearshore farming were made without enough science‐based evidence. Now, with more scientific knowledge, this review revisits past predictions and expectations of offshore aquaculture. We analysed and explained the oceanographic features that define offshore and nearshore sites. Using Atlantic salmon (Salmo salar) as a case study, we focussed on sea lice, amoebic gill disease, and the risk of harmful algal blooms, as well as the direct effects of the oceanography on the health and physiology of fish. The operational and licencing challenges and advantages of offshore aquaculture are also considered. The lack of space in increasingly saturated sheltered areas will push new farms out to offshore locations and, if appropriate steps are followed, offshore aquaculture can be successful. Firstly, the physical capabilities of the farmed fish species and infrastructure must be fully understood. Secondly, the oceanography of potential sites must be carefully studied to confirm that they are compatible with the species‐specific capabilities. And, thirdly, an economic plan considering the operational costs and licencing limitations of the site must be developed. This review will serve as a guide and a compilation of information for researchers and stakeholders.

Veterinary Medicinal Products (VMPs) are used in intensive aquaculture production to treat a wide range of bacterial and parasitic infestations. Their release into the environment poses concerns regarding their potential ecotoxicological risks to aquatic ecosystems, which need to be evaluated making use of appropriate Environmental Risk Assessment (ERA) schemes and models. This study presents an overview of the major aquaculture production systems in Europe, the VMPs most commonly used, and the environmental quality standards and regulatory procedures available for their ERA. Furthermore, it describes the state-of-the-art on the development of environmental models capable of assessing the fate, exposure, ecotoxicological effects and risks of VMPs in aquaculture production systems, and discusses their level of development and implementation within European aquaculture. This study shows that the use of environmental models in regulatory ERA is somewhat limited in many European countries. Major efforts have been dedicated to assess the fate and exposure of antiparasitic compounds in salmonid cage systems, particularly in Scotland, while models and scenarios for assessing dispersal of antimicrobials, in general, and antiparasitic compounds in the Mediterranean as well as in Scandinavian regions are less available. On the other hand, the use of ecological models for assessing the effects and risks of VMPs is almost absent. Recommendations are provided to improve the chemical exposure and effect assessments and the ecological realism of the modelling outcomes, paying special attention to the protection goals set for the regulatory ERA of VMPs in Europe.

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