Dartmouth researchers have developed a sustainable feed for aquaculture, focusing on Nile tilapia, by using a marine microalga co-product as a replacement for traditional fishmeal. This comes at a crucial time as aquaculture, the world's fastest-growing food sector, faces environmental challenges. The industry relies heavily on fishmeal and fish oil, which are sourced from small ocean fish essential to marine ecosystems. With demand for these resources expected to outstrip supply by 2040, and additional environmental concerns arising from the use of soy and corn, there's a pressing need for sustainable alternatives.

The Dartmouth team's solution involves replacing fishmeal with a co-product of the marine microalga Nannochloropsis oculata. This microalga is rich in essential nutrients like protein and omega-3 fatty acids, making it a promising substitute. The co-product is the residual algae meal left after oils have been extracted for various commercial applications. It's available at a commercial scale, and its supply is expected to increase, offering a sustainable and scalable solution.

In their experiments, the researchers found that replacing 33% of fishmeal with the microalga co-product resulted in similar growth rates, feed conversion ratios, and survival rates in Nile tilapia. However, the study also indicated that the co-product had lower overall digestibility compared to whole cells, suggesting that further enhancements, possibly through enzymes, could improve its efficacy.

The study builds on earlier work that also aimed to make aquaculture feeds more sustainable by using different types of marine microalgae. Lead author Pallab Sarker notes that the research offers "new insight" into developing a sustainable approach to aquaculture. The team is now working on combining Nannochloropsis co-product with other marine microalgae to further improve the sustainability of aquaculture feeds.