Aquaculture looks for ways to secure the future supply of protein

More and more people want to eat seafood at the same time as wild stocks in the oceans are shrinking. Can new types of aquaculture be the solution to the future food crisis?

The world’s population is growing and the need for sustainably produced protein is rapidly increasing. Now significant research resources are being invested to find new and sustainable ways to cultivate seafood, both in the sea and on land. Cultivating fish and seafood is a rapidly growing industry worldwide, but today’s farming techniques can also have a negative impact on the environment. To create sustainable marine aquaculture requires finding solutions to two major challenges. These have to do with the nutrients that leak out from fish farms to the ocean and the feed, which traditionally has consisted of fishmeal from fish caught in the wild.

In August last year 1,200 catfish fry from Iceland arrived at the Department of Biological and Environmental Sciences. The fry, which weighed only 5 grams on delivery, have grown considerably, and now the largest weigh 150 grams. The fish are being studied to find workable methods for commercial farming of catfish and other marine species.

“We’re testing various ways to see how to raise the fish in a manner that is optimal for both the environment and the fish”, says Snuttan Sundell, professor of animal physiology and director of SWEMARC, the Swedish Mariculture Research Centre, which coordinates all research on aquaculture within the University of Gothenburg.

Catfish is an exclusive and sought after edible fish that has not yet been grown commercially on a large scale. The farming experiment is just one of several projects that aim to find ways that would facilitate the development of sustainable aquaculture. In addition to developing cultivation procedures for new marine species, much of the research involves testing different types of circular aquaculture systems and developing new types of feed.

The majority of fish farming in Sweden takes place today in what is known as open systems in fresh water. SWEMARC is working to find sustainable solutions for marine aquaculture. To have better control of both the water leaving the facility and the water in which the fish live, different forms of more closed farming systems are being tested. Studies show that as much as 60 per cent of the nitrogen from conventional fish farming is released directly into the water without being put to good use. Consequently, measures are needed to raise fish in a sustainable manner.

Clean water is a prerequisite for workable aquaculture. Among other things, microbiological filters are used to purify the water in recirculating aquaculture systems.
“There are not yet many marine recirculating farming systems that are commercially viable and thereby economically sustainable. That’s why this research is particularly important”, Snuttan says.

In Kristoffer Stedts’ degree project, he examined the possibilities of balancing nutrient emissions from a fish farm in Norway using algae and mussels.

Another method to reduce the effect of nutrient leaching from aquaculture involves raising several different species together in what are known as multitrophic systems. For example, algae and mussels can be grown in connection with a fish farm to ingest nutrients from the water and build it into their biomass. A master’s degree project by Kristoffer Stedt demonstrates that the technique seems to work, but that there are also practical challenges. In his degree project on marine biology, he examined the possibilities of balancing nutrient emissions from a fish farm in Norway using algae and mussels.

Blue mussels filter water and ingest the particulate nutrients, while the algae ingest the dissolved nutrients.
“We got good results. The mussels ingested between 15 and 30 per cent of the particulate substances, and the algae ingested 60 to 70 per cent of the nitrogen”, Kristoffer Stedt says.

An additional bonus is that the algae and mussels form a biomass that can be harvested and used for human food or animal feed and in this way create circular systems. One problem, however, is that very large algae cultivation is required to balance the nutrient leaching from large-scale fish farming, where large amounts of nutrients are produced.

Another part of the research surrounding multitrophic farming systems deals with developing farming methods for sea cucumbers and polychaete worms. These are animals that feed on bottom sediment and ensure that seabeds do not become anoxic. If they are raised together with a fish farm, they also contribute to ingestion of nutrients from the water, and a circular flow of nutrients can be created because these animals can also be used for fish feed or human food.

Development of sustainable marine feed for fish and crustaceans is another important area of research where there is a lot going on right now. Snuttan has conducted research in the area for more than 20 years, and he believes that we have come a long way with salmon feed, where a large proportion of fish meal has been replaced with vegetable feed.

“When it comes to marine species that have other requirements, we have not advanced as far. Here we’re looking at the possibilities of using marine plant foods like algae, but also bivalves, ascidians and other marine biomasses that can be grown.”

Although there is great potential for increased marine aquaculture in Sweden, Snuttan Sundell thinks we probably have a long way to go before we can compete with countries like Norway when it comes to volume production. A better way to go is to focus on smaller and sustainable local farms with high quality, perhaps with more exclusive species such as catfish and lobster.

“The key to success lies in sustainable, circular farming on a smaller scale. It can create new industries for local communities along the coast when fishing quotas are decreasing.”

Technological developments in aquaculture have taken a big step forward in recent years, but another obstacle to more large-scale farming is current regulations in this area. In SWEMARC, which is an interfaculty centre, natural and social scientists are actively working together to simplify and speed up the processing of permits for aquaculture.

“There are many entrepreneurs who want to invest in sustainable farming, but today’s regulatory system has not kept up with technological developments”, Snuttan says.