OYSTER AND FISH INTEGRATED AQUACULTURE IN EARTHEN PONDS FOR PRODUCTION AND ENVIRONMENTAL CONSERVATION

Maria Emília Cunha, Hugo Quental-Ferreira, Laura Ribeiro, Florbela Soares, Pedro Pousão-Ferreira

IPMA, Aquaculture Research Station, 8700-194 Olhão, Portugal

e-mail: micunha@ipma.pt

Key words: IMTA, Crassostrea gigas, Crassostrea angulata, nutrient credit, ecosystem services

Production costs of semi-intensive fish aquaculture in earthen ponds can be too high to offer sustainable economic activity. The production density is <1 to 3 kg per m³ and, given the energy costs, feed, losses due to theft, predation and diseases, the profitability is low. A possibility to improve the output with higher profitability and risk reduction is to integrate the culture of fish with oysters in the same earthen pond. Growing filter-feeders, like oysters, in fish ponds can result in a more balanced system in the earthen pond since the excess of phytoplankton resultant from nutrient excretion and the particulate organic matter from fish faeces and slopping feeding are controlled by oysters that use this organic matter to grow. Pond dissolved oxygen levels are more stable and the water quality is better improving fish body condition. At the end, there is increase in the system productivity, lower expenditure and higher product diversification.

The increase in profitability of these systems in addition to the nitrogen and phosphorus reduction (bio-mitigation) allow the creation of wetlands with a dual purpose that will incorporate both conservation and aquaculture production attracting new investments in ecosystem services and contributing to the recovery of degraded coastal areas.

This presentation will refer 6 years of this kind of IMTA practices in Portugal and will answer, among others, to questions like:

What are the best structures and densities to grow oysters with fish in ponds?

How can oysters affect fish production and water/sediment quality?

Can oysters achieve similar growth performance and organoleptic quality than in the wild?

How much economic growth can oyster-fish IMTA in ponds allow?