A thesis from the University of Gothenburg proposes kelp fly larvae and marine yeast as suitable alternatives to fishmeal and soybeans in feed. These two raw materials can be produced using byproducts from the seafood industry, which would otherwise be discarded. The fly larvae and marine yeast have over 50% high-quality proteins and high levels of beneficial omega-3 fatty acids that fish need to grow and thrive – ultimately providing healthy food for humans.

“Both the fly larvae and the yeast have good nutritional values, and I noticed that the fish had a healthy appetite for the feed,” said Niklas Warwas, a doctoral student at the University of Gothenburg. “Another important benefit is that such feed ingredients can strengthen the immune system and thereby protect the fish from diseases.”

The focus of Niklas’s thesis is on investigating the opportunities for more circular food production that reduces environmental and climate impacts. The marine yeast was cultivated in nutrient-rich brine from the herring processing industry. This brine is a byproduct that currently represents a cost for the industry, as it has to be treated before being discharged into the environment. The water could now be reused to produce a new raw material for fish feed instead. Similarly, kelp flies were fed on a residual product from algae cultivation.

One important advantage is that neither the yeast nor the fly larvae require significant further processing before they can be used as raw material in fish feed, which can reduce the energy consumption of feed production.

“Both the yeast and the insects can be cultivated on a wide range of different organic materials. It is important to create local circular systems where the fish feed can be produced close to the processing factories, which in turn can be located close to the fish farms. This reduces transportation requirements and makes these alternative feed ingredients more competitive.”

“My research can help Sweden achieve more circular food production, in which by-products are reused instead of being discarded. This contributes to a more resource-efficient food industry, which is important when access to arable land and clean water is under threat and the population is growing,” Niklas concluded.

Thesis: Novel Marine Ingredients for Aquaculture – Fish Nutrition, Physiology and Intestinal Health