Integrated multitrophic aquaculture (IΜΤΑ) is an innovative mariculture methodology that reduces the environmental footprint and increases the profitability of the farm. It combines the cultivation of species belonging to different trophic levels, simulating a natural food web. In this study, five Mediterranean species were co-cultured in three operating fish farms in the Aegean (E. Mediterranean) Sea with different trophic conditions. The co-cultivated species were sea bream (Sparus aurata), European sea bass (Dicentrarchus labrax), Mediterranean mussel (Mytilus galloprovincialis), rayed pearl oyster (Pinctada imbricata radiata), and sea cucumber (Holothuria polii). Bream, bass, and mussels were cultivated according to the traditional on-growing methods (fish cages and longlines), whereas the pearl oysters and sea cucumbers were cultivated in baskets designed specifically for oyster farms. To estimate the growth of the co-cultivated species, growth indicators were calculated using length and weight measurements. Furthermore, the growth measurements from co-cultivated species were compared to the respective ones from natural populations. All the species showed high survival rates in the integrated multitrophic aquaculture (IMTA) conditions. Pearl oysters and Mediterranean mussels had positive growth in fish farms with high concentrations of nutrients. Mussel condition index (CI) was 42% in Aquaculture 1 (Aq1) and 33% in Aquaculture 2 (Aq2), compared to 35% in a typical Mediterranean mussel farm. Pearl oysters CI in Aq1 was 53%, in Aq2 56%, in Aquaculture 3 (Aq3) 19%, and in natural populations ranging from 30% to 45%. In contrast, holothurians did not gain weight under the fish cage regime despite the high survival rate. Their final total weight was 17.3 g in Ag1, 8.3 g in Aq2, and 18.3 g in Aq3, but in the natural population, the mean weight was 80 g.
Ιntegrated Multitrophic Aquaculture (IΜΤΑ) is an innovate marine fish culture methodology that reduces environmental footprint and increases profit. It is a method that combines cultivation of species belonging to different trophic levels simulating a food web. In this study, three species Mediterranean species were co-cultured (sea bream Sparus aurata, Mediterranean mussel Mytilus galloprovincialis and pearl oyster Pinctada imbricate radiata), in three operating fish farms in Aegean, Mediterranean Sea with different trophic conditions. Sea bream and mussels were cultivated according to the standard growing methods (fish cages and longlines), while the pearl oysters in baskets. Both mussels and oysters were grown near the fish cages in 2-4 m depth. The oysters showed a positive growth rate in all 3 fish farms. In contrast, mussels could not benefit from the fish farm effluents in all areas and their growth reflects on the physicochemical characteristics of the area. Thus, the bigger growth rate of the mussels were observed in the mesotrophic fish farm. The above preliminary results are very promising and may became the motivation for experimental IMTA cultures with more and different species.
The fast growth of the marine aquaculture industry has caused major concerns regarding its environmental impacts and particularly the direct discharge of organic wastes into sensitive marine ecosystems. Aquaculture effl uents are rich in nitrogen compounds that may enhance local primary productivity, leading to the development of algae blooms. IMTA (Integrated Multi-Trophic Aquaculture) systems can improve sustainability by exploiting wasted nutrients and particles from aquaculture there by providing simultaneously economic and environmental benefits. Seaweed Ulva rigida has been proposed as an excellent species to use in IMTA. In the present study an IMTA suitable methodology for cultivation of U. rigida is assessed, in terms of seaweed survival and growth. The experiment was run for 17 days in two different coastal sites in Heraklion, Crete and the results showed that in the site with limited anthropogenic disturbance the seaweed was successfully cultivated with a significant growth in both maximum length and biomass.
The commercial value of Holothuria is constantly rising, and the increase in fishing pressure has resulted in high risk for wild populations. In this context, farming of these species could increase the supply to the market thereby relaxing pressures on wild populations. The use of sites in the vicinity of fish farms could have a double benefit i.e. the use of organic material precipitating from fish cages as a food source and the decrease of wastes released to the benthic environment. The use of holothurians in integrated multi-trophic aquaculture (IMTA} has been attempted in various parts of the world since these deposit feeders are suitable species for consuming unused feed pellets and fish faeces. Tentative results from experimental cultures in the Aegean have shown a promising future for holothurian-based IMTA, although more research is needed to refine the methodological aspects involved.