New fish-free aquaculture feed to raise fish farming standards

Nov. 12 (UPI) -- Scientists have developed a new fish-free aquaculture feed that is cheaper, healthier and more eco-friendly than traditional feeds.

The new feed, which doesn't use any fish meal or fish oil ingredients, helped fish gain weight faster and resulted in a more nutritional fish filet.

Researchers detailed the feed's advantages in a new paper, published Thursday in the journal Scientific Reports.

"This is a potential game-changer for shifting aquaculture to more sustainable practices," lead study author Pallab Sarker, a sustainable aquaculture scientist at the University of California, Santa Cruz, said in a news release.

Farmed fish help reduce pressures on wild fish stocks, but the benefit is partially negated by aquaculture's reliance on wild-caught forage fish for fish feed ingredients.

To build a healthier, more eco-friendly feed, Sarker and his colleagues turned to algae.

Scientists were able to replace the fish oil normally used to make fish feed by substituting whole cells from a marine microalga called Schizochytrium sp.

To replace fish meal, researchers used biomass from oil-extracted marine microalga called Nannochloropsis oculata, a waste material leftover from commercial omega-3 dietary supplement production process.

Researchers used the new feed to cultivate 480 Nile tilapia for six months.

Compared to tilapia from the control group, tilapia on the fish-free diet exhibited 58 percent greater weight gain percentages. The tilapia raised on the fish-free feed also boasted greater levels of heart-healthy DHA omega-3 fatty acids.

"You can develop fish-free feed using soy and corn and other ingredients, but the problem is, you compromise the fatty acid profile of the filet," Sarker explained. "Terrestrial vegetable oils lack long-chain omega-3 fatty acids, but from the combination of these microalgae, we found a higher amount of deposition from DHA into tilapia filets, which is good for human health."

Alternative fish feeds created using agricultural crops have previously succeeded in replacing fish meal and fish oil ingredients, but have failed to generate acceptable weight gains or nutritional values.

The latest feed bests agricultural-derived feeds without requiring the use of farmland, making it more sustainable. The new feed's use of waste material also makes it more economically viable than crop-derived fish feed alternatives.

While the new fish feed is a bit more expensive to produce than traditional fish-derived feeds, scientists hope the feed's ability to generate better weight gains in tilapia will generate interest in the aquaculture industry.

"Aquaculture is the fastest growing food sector in the world, but it's still a young industry compared to agriculture," Sarker said. "We have an opportunity to not make the same mistakes. This research could be a key leverage point for reforming aquaculture to ensure sustainable growth in ways that don't damage terrestrial or aquatic ecosystems."