Salmon breeding comes ashore

Fish farming is currently one of the world's fastest growing food industries. Denmark has a long tradition of fish farming and today is among the world leaders in equipment for green production, thanks to the development of so-called model fish farms. The high-tech and environmentally friendly model fish farms use water from boreholes, rather than from rivers, and are based on water recirculation technology. This means that the fish farm recycles as much as 95 percent of the water instead of merely letting it drain away into the countryside.

Now DTU Aqua and several of the key players in the industry are joining forces to take Danish fish farming a stage further. In order to put large rainbow trout and salmon on the menu as well, the so-called model fish farms are to be expanded to include the breeding of saltwater fish as well as freshwater fish -- and it is to take place inland. The project is being supported by the Ministry of Food, Agriculture and Fisheries' Green Development and Demonstration Programme (GUDP).

"The global salmon market is huge. The production of fish in the aquaculture industry is increasing in several countries, but so far Denmark has not increased production significantly, mainly because of environmental restrictions,. But why should the Norwegians produce our salmon if we can do it just as well -- and without compromising the environment?" asks technical project manager Per Bovbjerg Pedersen, from DTU Aqua in Hirtshals.

More fish, less pollution In order to increase production in a sustainable and profitable manner, we need cross-disciplinary collaboration on new technological solutions for breeding fish in salt water to complement those solutions that DTU Aqua has already helped to develop within the field of freshwater fish breeding.

"The goal is to produce more fish, but with the same or even lower emissions of nitrogen out into the environment. This will be done partly through applying a known technique in freshwater farming, whereby bio-filters are used to convert the ammonia excreted by the fish into nitrate. Now the goal is to develop the technology to do the same with salt water, in order to convert this nitrate into nitrogen which can be released as a harmless gas. In this way the nitrogen is removed safely from the water," explains Per Bovbjerg Pedersen.

In a four-year project supported by the Ministry of Food, Agriculture and Fisheries' Green Development and Demonstration Programme (GUDP), DTU Aqua, in collaboration with key industry players, is to develop technology to enable large rainbow trout to be farmed inland in salt water. After two years, the project will be expanded to test the feasibility of farming Atlantic salmon in inland saltwater fish farms.

DTU Aqua is responsible for the professional management of the project, in particular the environmental impact, water quality parameters and the development and optimization of cleaning technologies. The work is being carried out at the North Sea Science Park in Hirtshals in collaboration with representatives from all relevant parts of industry including the leading Danish food producer Biomar and the largest breeding, processing and sales company AquaPri.

The goal in the long term is not only to create a basis for the Danish production and export of sustainably produced saltwater fish: the actual technology itself will have equally strong export potential, Per Bovbjerg believes.

"Denmark is already a world leader in water recirculation technology and model fish farms, thanks to our unique composition of components drawn from our experience in water recirculation techniques. The aim is to further exploit and expand the Danish position in the field of water recirculation by combining it with breeding techniques, equipment and complete plant solutions for saltwater fish farming," says the technical project manager from DTU Aqua.

What is a model fish farm? The high-tech and environmentally friendly model fish farms for breeding fish use water from boreholes and are based on water recirculation technology. This means that a farm recycles as much as 95 percent of its water. A comprehensive measurement and documentation project to monitor the environmental impact of model fish farms was started in 2005. The project was based among other things on DTU Aqua's know-how about fish farming systems, including water recirculation technology.

Today, model fish farms are located in large concrete plants on the traditional fish farms sites. But as the model fish farms do not need the water from the streams, the streams are now free of obstacles such as dams and barriers. This also provides free passage for the wild fish on their way to and from spawning grounds and the sea, which is beneficial for wild fish stocks.

Today the aquaculture industry -- both inland and sea-based fish farms -- is the world's fastest growing food industry.