Researchers at Bremerhaven University of Applied Sciences are working on trout feed from local resources

Mealworms and algae oil could make aquaculture more sustainable

Aquaculture has been the fastest growing sector in food production worldwide for years and could make a significant contribution to food security for future generations. However, feeding fishmeal is not optimal, both economically and ecologically. In the ‘LokaLaStern’ project, researchers at Bremerhaven University of Applied Sciences therefore want to develop a nutrient-optimised feed for trout that comes entirely from regional sources. The project partners are the Alfred Wegener Institute in Bremerhaven and the Research Institute of Feed Technology at IFF e.V. in Braunschweig. The project is funded by the Federal Ministry for Economic Affairs and Climate Protection as part of joint industrial research.

According to the Federal Statistical Office, an average of 13.4 kilograms of fish ended up on German plates per person in 2023 - and the trend is rising. At the same time, fish stocks in domestic waters are dwindling due to overfishing, environmental pollution and the effects of climate change. The rearing of fish in so-called net pens is also associated with environmental damage. An alternative to this is aquaculture, in which the water is purified and reused so as not to further pollute the environment. But even these are not currently working optimally. ‘A significant environmental and economic problem in aquaculture today is that it remains heavily dependent on fishmeal as a protein source and fish oil as a fat component. As fishmeal and fish oil are finite resources, their prices are rising continuously,’ says Prof Dr Rainer Benning from Bremerhaven University of Applied Sciences. The alternative soya used also causes environmental problems, such as the cultivation of genetically modified soya, deforestation of the rainforest and the conversion of forest areas into agricultural land, which leads to an increased CO2 footprint due to transport.

In the ‘LokaLaStern’ research project, the researchers want to optimise the feed for trout in aquacultures. They want to develop a production process in which the raw materials come from local sources such as mealworm larvae. This also involves enriching the insects with the amino acids methionine and lysine through targeted feeding. ‘When it comes to alternative protein sources, the use of insects is relatively new. In order to minimise the currently necessary addition of expensive individual amino acids in animal feed, it is possible to influence the amino acid composition and the fatty acid spectrum of insect larvae by selecting a suitable substrate for feeding in such a way that these are specifically accumulated in the protein. Regional side streams, for example from the food industry, are to be utilised and upgraded in terms of the bioeconomy,’ explains Prof. Benning. The researchers at the university have already gained initial experience in past research projects with feeding insects with by-products from the food industry that would otherwise end up as waste. In addition to adapted insect protein, regionally produced pulses such as peas or lupins and alternative oil sources such as algae are to be among the ingredients of the fish feed.

An important aspect in the question of how environmentally friendly an aquaculture system is is the water quality. If the water is too polluted, fresh water must be added. The feed must have certain physical properties in order to minimise the water requirement and be well absorbed by the trout. Pellet stability is particularly important, as is the sinking behaviour. This is where the researchers want to make use of the stabilising properties of starfish meal. The project will determine the optimum admixture rates. This should also minimise the loss of nitrogen and reduce the abrasion that leads to pollution of the recirculating water. ‘The project improves existing freshwater aquacultures and serves to develop a new product, especially for rearing trout in recirculating aquacultures using regionally produced feed raw materials. This increases the attractiveness of the project, particularly for small and medium-sized companies,’ says Prof Benning. 
The research project ‘LokaLaStern - A feed production process for trout in recirculating aquaculture systems based on alternative local resources such as mealybug larvae and starfish’ is funded by the German Federal Ministry for Economic Affairs and Climate Protection as part of joint industrial research. The project has a total volume of 713,924.96 euros. 213,924.96 euros of this amount is attributable to Bremerhaven University of Applied Sciences.

(Translated with the support of deepl)