Environmental impact of fast growing aquaculture sector

Published: 13 January 2020

Aquaculture is the fastest growing food-producing sector and now accounts for 50 percent of the world's fish that is used for food. With a growing world population to feed, the importance of aquaculture as a source of protein is going to increase. This is likely to produce conflicts between two important sustainable development goals: SDG 2 (Zero Hunger) and SDG 14 (Life below water).

Integrated Multi-Trophic Aquaculture facilitated

Integrated Multi-Trophic Aquaculture (IMTA) is seen as a technology that could diminish negative effects on the environment and boost production. IMTA farmers combine species that need supplemental feed such as fish, with “extractive” species, which use the organic and inorganic materials and by-products from other species for their own growth and act as living filters.

The idea is good, but the development of actual working IMTA farms is still in its infancy. The IMTA concept, in the strictest sense, is having different trophic levels integrated into one farm or business, at the same site. However, trophic links in aquatic ecosystems can extend over a large spatial scale. As aquaculture heads towards more organised spatial planning, IMTA can also be realised with single-species farms and sound ecosystem-based management. Within the EU project IMPAQT Deltares is developing tools to facilitate the development and implementation of IMTA.

Six indicative test sites

To test the new technology as well as assess the environmental and socio-economic value of the IMTA approach there are 6 indicative test sites, ranging from small research sites to industrial production sites and from inland to coastal to offshore marine sites.

The pilots comprise:

Keywater, Ireland This is an inland site with freshwater, combining European perch with common duckweed and Tench with various species of algae.
SAMS UK This is a coastal site with various seaweeds and shellfish.
Marine Institute, Ireland This is a coastal site with salmon and lumpfish, lobster and seaweed.
YSFRI, China This is a large site combining several species of seaweed and shellfish.
NSF, the Netherlands This is an offshore test site with seaweed and mussels.
ÇAMLI, Turkey This is a large offshore site with European seabass, black mussels and sea lettuce (a seaweed).

The inland IMTA site at Carrick-on-Shannon (Ireland). Foreground, pond with perch, background purification with duckweed.

Methodology and modelling

Deltares is developing the advanced IMTA model, which relies on our new Delft3D Flexible Mesh modelling technology for hydrodynamics, nutrient dynamics, primary and secondary production. Within IMPAQT we have developed a seaweed module that runs in DELWAQ (computational kernel of the D-Water Quality module of the Delft3D FM Suite) and can compete for nutrients in the ecosystem with microalgae. Shellfish growth is modelled using Dynamic Energy Budget modelling, that is also integrated in the ecosystem model. The first site that has been modelled was the Dutch North Sea Farm. This showed that the model worked, but because the site is very small and offshore with a huge amount of water exchange, the environmental effects (and hence the benefits of IMTA) are tiny. The model is now going to be used for upscaling scenarios for NSF and will also be applied to the ÇAMLI site. This is a large industrial site and we expect much more distinct effects of IMTA here.

Another role of Deltares is to develop a methodology to quantify ecosystem services of IMTA. The model results can be used as input, as well as many other types of data.

Oban, site visit to the experimental seaweed farm (Scotland)



Management platform enabling sustainable IMTA production

IMPAQT  is a project funded by the European Horizon 2020 programme aimed at promoting and supporting the eco-intensification of aquaculture production systems: inland (including fresh water), in the coastal zone, and offshore. IMPAQT aims to develop and validate in-situ a multi-purpose, multi-sensing and multi-functional management platform for sustainable IMTA production. ​

Two distinct decision-support systems are developed and tested. The Integrated management system (IMS) is designed for optimised direct management of farms and relies strongly on sensors, remote sensing and information such as weather forecasts, wave forecasts etc. The other system is an advanced, ecosystem-based IMTA model, which is intended to be instrumental in planning and permitting.

Optimising lay out, licensing and communication of IMTA

The IMPAQT project has been recently assessed by the European commission and received a very positive review. The general opinion is that ecosystem-based management is the key to getting IMTA working and profitable. the IMTA model is going to be a very important instrument, not only in optimising the lay-out of farms relative to each other, ensuring that extractive aquaculture can optimally access waste nutrients from fish farms, but also in facilitating licencing systems. The current permitting and licencing procedures are geared towards single-species farms. The models and the ecosystem services assessment can be instrumental in providing evidence to regulators that negative environmental impacts are minimal. This will not only require further development of the modelling technologies, but also ways to clearly communicate the underlying science and methodologies to non-specialists to create sufficient faith in these new techniques.






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