Frontiers in Marine Science (May 2014)
Modelling for an improved integrated multi-trophic aquaculture system for the production of highly valued marine species
Abstract
Integrated multi-trophic aquaculture (IMTA) is regarded as a suitable approach to limit aquaculture nutrients and organic matter outputs through biomitigation. Here, species from different trophic or nutritional levels are connected through water transfer. The co-cultured species are used as biofilters, and each level has its own independent commercial value, providing both economic and environmental sustainability. In order to better understand and optimize aquaculture production systems, dynamic modelling has been developed towards the use of models for analysis and simulation of aquacultures. Several models available determine the carrying capacity of farms and the environmental effects of bivalve and fish aquaculture. Also, in the last two decades, modelling strategies have been designed in order to predict the dispersion and deposition of organic fish farm waste, usually using the mean settling velocity of faeces and feed pellets. Cultured organisms growth, effects of light and temperature on algae growth, retention of suspended solids, biodegradation of nitrogen and wastewater treatment are examples of other modelled parameters in aquaculture. Most modelling equations have been developed for monocultures, despite the increasing importance of multi-species systems, such as polyculture and IMTA systems. The main reason for the development of multi-species models is to maximize the production and optimize species combinations in order to reduce the environmental impacts of aquaculture. Some multi-species system models are available, including from the polyculture of different species of bivalves with fish to more complex systems with four trophic levels. These can incorporate ecosystem models and use dynamic energy budgets for each trophic group. In the proposed IMTA system, the bioremediation potential of the marine seaweed Gracilaria vermiculophylla (nutrient removal performance) and the Mediterranean filter-feeding polychaete Sabella spallanzanii (capacity to filter, accumulate and remove particles and bacterial groups) co-cultured with the highly valued marine fish Diplodus sargus is assessed. This study includes to development of a model to mathematically describe the proposed IMTA system. The main focus of this model is optimize species combinations and yields from each trophic level. Such a mathematical description of the system also opens the possibility of developing simulators to study the purposed system, comparing it under different conditions.
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