Integrated Multi-Trophic Aquaculture represents a polyculture system. In fact, until recently, fish production has been carried out under monoculture conditions. In IMTA several species are produced in such a way that invertebrates and macroalgae can recycle waste substances deriving from the culture of vertebrates (fish). This new vision has led to the development of the concept of circular economy, where wastes from a production process are used for another production process. In applying this fundamental concept, industry is a double benefit of waste reduction and additional biomass production.
The concept of IMTA can be a valuable tool to ensure the economic and environmental sustainability of the aquaculture industry. However, there is a clear need for further developments before its large-scale adoption across Europe because many barriers still hinder the full acquisition of IMTA. The conditions are not yet fully in line in Europe for the large-scale adoption of IMTA systems, although there is a growing commercial interest and considerable environmental awareness. A consumer survey has shown that there is a willingness to pay a supplement for a final product obtained using an IMTA system, but to achieve this, it is necessary to develop a set of production standards to be used to increase consumer confidence in the concept of IMTA and to protect producers’ investments in the IMTA system.
The use of biofilter modules (structures in which extractive organisms were reared) around the cages, was one of the first researches in the field of environmental bioremediation at a European level that involved research entities operating at different latitudes, from Atlantic to Mediterranean systems, in which a difference of bioremediator species has emerged and also a selection of the possible species to be used, polychaetes and ascidians in the northernmost systems and even madrepores in Israel.
A very important point emerging from this project was the identification of these structures not only as a source of environmental bioremediation, but also as a source of attraction of many fish species near the cages, generating areas of high fishing. In these pioneering projects the efficiency of the filtering organisms grown on specific modules has been amply demonstrated, but it has also been highlighted a great problem that prevented its implementation, that is the huge amount of biofilter biomass necessary for an efficient bioremediation, a biomass for the most part made up of non-edible organisms which itself represented a “waste” to be disposed.
Hence the need to introduce “new” biorimediator organisms producing a biomass (by-product) of high commercial value to be used in various sectors such as sport fishing, aquariums, feed and pharmaceutical industry.
The advantages of the IMTA include:
-Recycling of waste,
-Minimization of impacts,
-Filtration of larvae of many parasites
-Creating new income streams.
The main problems concern:
– The spatial location (concessions):
To significantly reduce nutrient waste from a plant, the filter and macro-algae component needs a lot of space producing logistical constraints for the location of the extractive component to be placed around the fish breeding cages, ensuring that these additional products do not hinder the logistical operations for the production of the main product. The company must be able to manage the system to a much wider extent, using the IMTA concept to balance the inputs and nutrient reductions at a scale of the entire body of water, rather than adopting an approach on an individual breeding site.
– Food security:
Companies must be able to certify their products, which should be better.
The development of the co-product market to ensure that the production of all components of the IMTA system is economically viable.
In the case of molluscs, the market is already well developed throughout Europe. In the case of algae this market is still very weak. The large scale adoption of IMTA across Europe could lead to the production of substantial biomass of algae, and it is essential that there is a market for these products.
To date, there are some plants in Europe that use this system at productive level, even if with several problems not yet resolved. However, most are located offshore with considerable depth under the breeding cages.
The proposed system provides for the first time at European level the use, in a combined way, of bioremediation organisms such as POLYCHAETES and PORIFERA in addition to the most commonly used MUSSELS and MACROALGAE, having a high tolerance to environmental stress conditions and better performances as bioremediators as already demonstrated during previous scientific research.