Around the world, fishermen catch less and less fish in the sea. So where does the fish we humans eat come from? More and more often they come from breeding facilities. Today, 50 percent of fish and shellfish and 96 percent of algae come from aquaculture farming. And these figures are expected to rise. This also means that more facilities and thus more aquaculture farming space will be required.
In Germany, aquaculture near the coast of the North Sea is not possible for two reasons: For one, the mudflat is a National Park and therefore protected. Secondly, the water is too cloudy in many places and contains too many particles to breed marine organisms. One alternative is to use offshore wind farms both for energy production and for aquaculture. Scientists at the Alfred Wegener Institute are conducting research on how this can be done in a sustainable way.
“In order to farm fish using aquaculture you have to consider more than just the size of the area you want to use. There are also many environmental aspects to think about,” explains AWI scientist Dr Britta Grote. Fact is, aquaculture has a relatively bad reputation – due to industrial fish farms in South America and Southeast Asia, where intensive fish and prawn farming has often damaged the surrounding countryside.
“Species, which are being fed, such as fish or crustaceans, release nutrients into the water, which can contribute to the over-fertilisation of the surrounding ecosystem. This problem could be solved by breeding species of algae and mussels that consume nutrients,” says Britta Grote. “They ingest these excess nutrients and thus maintain a nutrient balance.”
Combined farming of species, which are being fed, and nutrient-eating species is called integrated multi-trophic aquaculture (IMTA). “We use a natural filter – algae – to make fish farming environmentally friendly. At the same time, the algae represent an additional source of income.” In short: IMTA means biological recycling with great economic benefits.
Sustainable, environmentally friendly, economical
As part of her research, Britta Grote therefore looks into multiple utilisation of offshore areas around wind farms in order for offshore aquaculture to be carried out in a sustainable, environmentally friendly and economical way in accordance with the IMTA concept. To put it simply, she investigates which algae, mussels and fish are suitable and how much breeding space is needed for which species in order to breed them in an environmentally friendly and economical way in the offshore region of the North Sea.
“Our research so far indicates that algae and mussels bred offshore usually grow well – and most of the time they are of a better quality than those bred nearer the cost,” says Britta Grote. Some of these algae species have a high utilisation potential: They are used by the cosmetics industry, the pharmaceutical industry and also as a healthy food.