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The feeding habits of Sparus aurata L., Diplodus annularis L. and Spondyliosoma cantharus L. in the Ria Formosa (southern Portugal) lagoon system were studied using three simple methods (frequency of occurrence, numeric percentage and percentage weight) and a composite index [index of relative importance (IRI)]. The Ivlev index was used to evaluate diet selectivity, while the Schoener overlap index was used to compare diets, and diet diversity was characterized by the Simpson index. The diets of the three species consist of a wide variety of food organisms, nevertheless S. aurata seems to be the most specialized. No significant dietary overlap was found, with S. aurata preferentially selecting gastropods and bivalves, while S. cantharus preferentially selected a wide variety of crustaceans and D. sargus a wider array, including crustaceans, gastropods and bivalves.

Environmental decision-making generally involves issues of complexity, uncertainty and information feedback. The complexity of environmental problems calls for integrated and multi-disciplinary approaches, which include civil society and stakeholder groups affected by or affecting environmental decisions. This paper presents a participatory modelling framework to facilitate public and stakeholder involvement in environmental decisionmaking. Results from a case study in the Ria Formosa Natural Park in Portugal illustrate the process of participatory modelling. The use of the System Dynamics modelling methodology facilitates the identification of the fundamental structure underlying the processing of information flows in order to achieve the desired behaviour of environmental decisions. It sets up a collaborative environment for the involvement of stakeholders in the development and experimentation of alternative policy scenarios. Along with the achievement of a simulation model, this approach is likely to foster trust in institutions, promote team learning and increase commitment towards actions.

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Regulation to minimize impacts from aquaculture is of key concern in coastal zone management for the sustainability of the industry and the receiving environment. Market and consumer forces are presently driving much of this regulation and its implementation. Mathematical modelling can provide the tools for planning and monitoring as well as regulation, and a number of countries have well‐developed policies and procedures in place which utilize modelling tools. The main impacts currently modelled are nutrient enhancement, organic waste deposition and the dispersion and deposition of medicines and chemicals. The release of these wastes is influenced by species‐ and site‐specific characteristics, as well as culture and husbandry techniques. The modelling process requires consideration of definitions and limitations; standards for model development including clear objectives and justification; good technical description; use of good and appropriate data; calibration; validation; sensitivity analysis; quality assurance; auditability and consideration of the operational needs of the user, the grower and/or the regulator. Models should have simplicity and clarity; be fit for purpose; be open to scrutiny; be accessible, user‐friendly and be used with caution. Current models are considered to be limited in scope but do cover the main hydrodynamic and particulate processes. The regulation and monitoring of finfish aquaculture involving the direct use of models is apparently restricted to relatively few countries where they are involved in setting holding capacity, the licensing of medicines and for assessing site applications. Different approaches have been developed in different countries as required. In contrast, many countries do make considerable indirect use of modelling techniques within the regulation process. With respect to shellfish, models are in current use to predict and optimize exploitation capacity but there is scope for studying nutrient flux, habitat degradation and deposition below suspended systems. Future developments for finfish need to better address the main question of holding capacity or exploitation capacity in relation to nutrients and medicines release, including whole water body/regional impacts. The relationship and predictability of toxic algal blooms remains some way off. Modelling the complexities of degradation, resuspension and the effect of the scavenging process on the transport of in‐feed medicines is required. Keys to future developments across Europe include accessibility, setting of Environmental Quality Standards or targets, training and support for users, resources and structured research.