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An aquaculture investor (AQI) index was developed in order to provide a broad view of the relative attractiveness of 29 different European countries to aquaculture investors. AQI is based on five complementary categories: Market, Production, Regulatory, Environment, and Social, with each category containing four indicators. The attraction of investment into aquaculture depends on the viability of developing aquaculture for each country, and these five categories account for the connectivity in the aquaculture industry. The index benchmarks and tracks countries' progress by producing a quantitative and scalable tool for stakeholders to assess and monitor aquaculture attractiveness, and is designed to rank aquaculture competitiveness for each country. Index scores calculated for Europe range from moderate to good, on a heuristic five-class scale. Countries in Northern Europe with well-established aquaculture sectors score better than countries in Southern Europe. Countries with developing aquaculture sectors tend to score moderately. While high scores within single categories can be achieved, the index rewards countries with high scores across the five categories, to provide a more useful tool for stakeholders. No countries within Europe rank below the middle of the moderate range. The index identifies several countries with high scores that do not have significant aquaculture industries (e.g. Sweden and Finland), and further research is warranted to identify why aquaculture has not been developed. It is expected that as AQI is expanded to lower income countries spanning other geographic regions, countries with lower quality indicator scores will have lower overall scores. The index provides a broad-scale approach across a wide range of categories, and should be interpreted in that context, since it is designed to provide high-level guidance of the general attractiveness for aquaculture in each country. Appropriate due diligence for specific circumstances is warranted by all stakeholders requiring further knowledge to assist decision-making. To ensure a wide dissemination and maximum visual appeal to both investors and the public, the AQI index was deployed as a smartphone application (AquaInvestor), freely available on the Google Play Store, together with a companion website, and to our knowledge provides the first country-wide comparative assessment of aquaculture potential, available to investors and the general public in eight European languages and Chinese.

Offshore aquaculture is the subject of intense debate, focusing on feasibility, sustainability, and the potential for effective expansion in the context of competing uses of the coastal zone, and a world requirement for an additional thirty million tonnes of aquatic products by 2050. A modelling framework that integrates the SWAT model for the watershed, Delft3D for ocean circulation, and the EcoWin model for long-term (10 year) ecological simulations, was developed for integrated analysis of catchment, inshore waters, and offshore aquaculture, providing an approach that addresses production, environmental effects, and disease interactions. This framework was tested using a case study in SE Portugal, for a system-scale modelling domain with an ocean area of 470 km2 and a coastal watershed area of 627 km2. This domain contains an inshore area of 184 km2 (Ria Formosa) subject to multiple (often conflicting) uses, including aquaculture of the high value (farmgate price > 10 € kg− 1) clam Tapes decussatus, and one of the first offshore aquaculture parks in the world, located at distance of 3.6 nm from the coast, at a water depth of 30–60 m, with an area of 15 km2. The park contains 60 leases, of which at most 70% are for finfish cage culture, and at least 30% for bivalve longline culture. A substantial part of the dissolved nutrients required to drive primary production that constitutes the food source for clams originates from the coastal catchment. Although stakeholder perception is that nutrients are mainly linked to point-source discharges from wastewater treatment plants, watershed modelling indicates that 55% of the nitrogen and 70% of the phosphorus loads are from diffuse sources. The residence time of waters in the inshore area is low (1–2 days), and consequently pelagic primary production takes place offshore, and drives inshore clam production. The longline culture of Mediterranean mussels (Mytilus galloprovincialis) in the offshore park reduces inshore food availability for clams: simulations suggest that a 3% decrease in clam yields will occur due to offshore mussel cultivation, at a cost of 1.2 million €. This is offset by revenue from offshore culture, but is a source of stakeholder conflict. Potential disease spread between the offshore and inshore systems was analysed using a particle tracking model, and allowed the development of a risk exposure map. This illustrates the challenges posed by hydrodynamic connectivity with respect to biosecurity of aquaculture and fisheries, both inshore and offshore. The model framework was also used for optimisation of stocking density, and analysis of combined culture of finfish and shellfish, both in terms of production and environmental effects. In the offshore aquaculture park, the models suggest that integrated multi-trophic aquaculture (IMTA) of gilthead bream (Sparus aurata) and Mediterranean mussels allows for an increased harvestable biomass of mussels, particularly at higher stocking densities, and offsets some of the negative externalities of finfish culture. By quantifying issues such as reduced yields for inshore stakeholders due to offshore activity, and illustrating the need for strong governance to offset disease risks, dynamic models make a valuable contribution in assessing the feasibility of offshore aquaculture, and the general principles that should underpin licensing and regulation of this sector. We stress the need to go beyond the conventional spatial planning toolset in order to ensure an ecosystem approach to aquaculture, and the opportunities that exist for applying a systems framework in an information economy, where the capital costs of software and data have been sharply reduced.

A multi-species model for shellfish polyculture in coastal embayments is presented, and an application of the model to a test site (Sanggou Bay, Northern China) used for large-scale longline cultivation of the Chinese scallop Chlamys farreri, the Pacific oyster Crassostrea gigas and the kelp Laminaria japonica is described. The model integrates a bay-scale ecological simulation with individual-based modelling of scallops and oysters, and upscales the individual processes for the target species (scallops and oysters) by means of a multi-cohort population dynamics model. Human interaction with the target cohorts over a number of years is explicitly simulated. The model has been used to estimate the exploitation carrying capacity for scallops and oysters in the system, the harvest potential for different seeding and harvesting scenarios, and the impacts on the ecosystem of different polyculture management strategies. Although an increase in seeding to 2 x and 15 x standard seeding for scallops and oysters respectively optimizes the yield of both, thus corresponding to the exploitation carrying capacity, the ratio of harvest/seed is lowered, which may make the fishery less attractive from an economic point of view. Progressive increases in seeding lead to a collapse of the fishery: this occurs at >15 x standard seeding for scallops, and at >30 x for oysters. In parallel, there are profound modifications at the ecosystem level, which were studied by means of a mass balance carried out on the model. Under standard conditions, there is a net export of primary production from the bay to the Yellow Sea, but at 15-20 x increase in seeding, the bay becomes a net phytoplankton importer, due to phytoplankton clearance by cultivated shellfish. The model simulates a period of 6 years in about 2 min, and was shown to be a useful tool for polyculture management over multiannual periods; a development of the socioeconomic component will allow feedbacks between economic consequences of different cultivation scenarios and ecosystem responses to be explicitly considered. The application of this type of model may be of use in promoting a more holistic approach to shellfish aquaculture management.