Resisting definitions
In Integrated Multi-Trophic Aquaculture, IMTA for short, low-trophic species like seaweeds and bivalves are farmed together with high-trophic species like salmon, where the excess nutrients of the fish are used as food and fertiliser by the others. While the concept offers an enticing vision of a balanced nutrient flow for aquaculture, defining the scope of an IMTA set-up is often the first stumbling block.
Some argue IMTA can be applied at the level of an integrated coastal area management (ICAM) strategy where the distances are larger, whereas others argue that the different species must be grown close to one another.
While exact definitions might help policymakers and regulators, Kane advocates looking at IMTA as a concept rather than a particular formula you apply. While the really solid results will be on the site level, for it to be effective you have to look a little bit bigger than exclusively the site.
“I definitely think we can manage IMTA on an area level,” said Kane. “The set of objectives are the key thing. Are we looking to reduce the impact of this farm on this local site, or in a broader set of circumstances? I think both answers are correct.”
Novel sensors and underwater communications
Within the project, new methods to measure and transmit data were pioneered, with applications that go beyond aquaculture. One is an underwater communications system. We struggle to connect wirelessly below the surface of the sea because electronic signals dissipate in water. To remedy this, researchers from the Tyndall Institute in University College Cork used ultrasonics to transmit data up to 100 metres.
At Tor Vergata University in Rome, scientists developed a prototype for a novel nitrite and phosphor sensor. Like a miniature lab in the field, it makes its measurements by passing chemicals and reagents through the tubes of a microfluidic chip, using lab-style titrations rather than light or electronics.
Putting it all together
In the Netherlands, the Deltares research institute created an IMTA model to assist farmers in the planning process of their site by helping them understand the flow of nutrients within the area. The model can also help regulators predict how aquaculture operations would alter the flow of nutrients and the balance of inputs and outputs at a broader level.
All of this data was then brought together in an intelligent management system, using data aquisition and a data aggregator that can handle the low power scenarios and unreliable connectivity found at the test sites. While software packages to manage a fish farm are relatively common, a monitoring dashboard that can track stock and welfare of species from the different trophic levels is novel, and vital to support the progression of IMTA farms. The Greek ICT company WINGS is now looking to bring to market the decision support system they developed within IMPAQT.
Sustainability and socio-economics of IMTA
Considerable attention was paid to sustainability and the socio-economics of IMTA across the 6 test sites in Ireland, Netherlands, Turkey, China and UK, especially with regards to the effects of adding algae to fish farms. On the ecological side, participants noticed a reduced risk of eutrophication and increased biodiversity.
On the financial side, IMTA offers a better use of production space and infrastructure, because more biomass is produced from the same site. On top of that, operators can exploit the seasonality of different crops, with seaweeds offering more regular harvests than for instance finfish.
Frank Kane is positive about the business aspects of IMTA: “In general, you can pretty much add IMTA to a monoculture site with relatively small costs compared to the overall cost of the site, and you can get a fairly satisfactory yield using what they call ‘non-ideal’ infrastructure. So you can actually get the benefits by having relatively simple technologies on site and seaweed and shellfish can act as an important remediation of fish waste in the environment.”
Future directions
If IMTA is to be a success in Europe, cooperation is the way forward, according to Kane. “I don’t think we should expect a salmon farmer to farm seaweed very well, or a seaweed farmer growing salmon very well. Site and infrastructure sharing seem like an ideal future IMTA model, with the different trophic farmers working together in adjacent operations, to their mutual benefit. It makes sense for producers of bivalves or seaweeds to cooperate with a finfish farm that has greater infrastructure and resources, while the finfish farm gets the benefit of the reduced impact and a more sustainable and environmentally friendly product.”
As the IMPAQT project has only just wrapped up, expect more IMTA papers to come out in the next few months. In the meantime, IMPAQT’s research efforts are being continued in the H2020 ASTRAL project, which brings in partners from Africa and South America. For people who would like to learn more about IMTA, IMPAQT’s handbook offers a good introduction, while the 8-hour MOOC dives deeper into the matter.