Multi-trophic aquaculture model: An approach to reducing environmental pressure in marine aquaculture in Quang Ninh
In the coastal areas of Quang Ninh, the rapid development of cage aquaculture has placed pollution pressure on the ecosystem. In order to reduce pollution from these cage-farming activities, Dr. Le Van Nam and his colleagues from the Hai Phong Sub-Institute of Oceanography - Institute of Oceanography carried out the project: “Research and proposal of solutions to reduce organic matter and nutrient pollution generated by concentrated cage aquaculture activities in the Quang Ninh sea area” (code: VAST07.05/24-25).
Dr Le Van Nam and colleagues conduct a field survey in a cage aquaculture area
The research team piloted an integrated multi-trophic aquaculture (IMTA) model combining marine fish, herbivorous fish, molluscs and seaweed. In the model, fish are the main cultured species and also the source of organic matter and nutrients; rabbitfish are placed in areas near the bottom to utilise material available in the bottom layer; oysters and mussels filter suspended particulate matter from the water; while seaweed absorbs part of the dissolved nutrients such as nitrogen and phosphorus. Organic matter and nutrients generated by fish farming are utilised by molluscs and seaweed for growth, thereby converting part of the material flow into biomass and contributing to reducing the amount of waste released into the environment.
Research area and locations of sampling sites
According to Dr. Le Van Nam, the results of the IMTA model trial showed that water quality improved markedly compared with traditional methods: the amount of ammonia decreased by approximately 16%, total phosphorus decreased by 16.9%, suspended solids decreased by 11.6%, and water transparency increased by an average of 0.10 m. In addition to reducing pollution and waste, IMTA also increases economic value by enabling farmers to harvest additional molluscs and seaweed from the same area.
The research team proposed three IMTA structures suitable for Quang Ninh: (1) Marine fish - Molluscs - Seaweed; (2) Marine fish - Molluscs - Benthic organisms - Seaweed; (3) Marine fish - Herbivorous fish - Seaweed. For effective application, the team proposed piloting the models in areas with high farming densities rather than implementing them on a large scale simultaneously, in close coordination with aquaculture zoning plans, the coordinating role of cooperatives and periodic environmental monitoring. At the same time, farmers need to receive support in terms of technical expertise, seed stock and conversion costs during the initial stage to minimise risks.
Translated by Tuyet Nhung
Link to Vietnamese version
