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Aquaculture Environment Interactions

    AEI prepress abstract   -  DOI: https://doi.org/10.3354/aei00375

    Integrated multi-trophic aquaculture systems: energy transfers and food web organization in coastal earthen ponds

    Sofia Gamito*, Hugo Quental-Ferreira, Aida Parejo, Joël Aubin, Villy Christensen, Maria Emília Cunha

    *Corresponding author:

    ABSTRACT: Three Ecopath models were built to reproduce the experimental treatments carried out in earthen ponds located in Olhão, southern Portugal, to understand the energy transferred and ecosystem state in integrated multi-trophic aquaculture (IMTA). These earthen ponds behave as simplified ecosystems or mesocosms, with well-defined borders, where the relationships between trophic groups can be described through ecosystem modelling. Different combinations of species were produced in these ponds, corresponding to the 3 treatments: (1) fish, oysters and macroalgae (FOM); (2) fish and oysters (FO); (3) fish and macroalgae (FM). The managed species were meagre Argyrosomus regius, white seabream Diplodus sargus, flathead grey mullet Mugil cephalus, japanese oyster Crassostrea gigas, and sea lettuce Ulva spp.. The results show that the total amount of energy throughput is 15 to 17 times higher when compared with an equivalent re-naturalized system. The high biomass and low recycling indicate an immature system with low resilience and low stability that demands high rates of water renewal and aeration to maintain good water quality levels for finfish production. The addition of oysters and macroalgae in the FOM treatment appeared to improve the water quality, since oysters control the excess of phytoplankton produced in the ponds by ingesting a good portion of the phytoplankton, while the macroalgae helps in the absorption of excess nutrients and create a good habitat for periphyton and associated macroinvertebrates. Some ecosystem attributes of the FOM ponds approached the values of the naturalized model, suggesting a possible path towards more sustainable aquaculture.