Dartmouth College scientists have created a more sustainable feed for aquaculture by using algae as a main feed ingredient. In a study published in PLOS ONE, an open-access peer-reviewed journal, the research team published several experiments substituting fish meal and fish oils with an algae-based byproduct called Nannochloropsis oculata (N. oculata), which is a protein-rich additive that could be a promising alternative to fishmeal. Opponents to aquaculture often cite overfishing of small-catch fish as one major drawback to the industry, making this algae-based substitute a major breakthrough for the industry.
Researchers have high hopes that further refining the aquafeed by adding enzymes to it that are likely to improve digestibility and increase nutrients available for absorption by the fish. In the long term, scientists hope the algae-based fishfood could completely eliminate the need for forage-fish-based fishmeal or fish oil in aquaculture feeds.
N. oculata is currently grown commercially, with byproduct oils used to manufacture biofuels and other products. It is considered to be a good source of omega-3 fatty acids, making it an ideal ingredient substitute for fish meal and fishoils that act as the main source of these fatty acids in fish food. Scientists have reported success in partially or totally replacing fish oil with vegetable oil in many farmed-fish species, but studies show that vegetable oil reduces the nutritional quality of the fish flesh. In recent lab tests, researchers ran experiments replacing fishmeal with algae-meal in varying percentages for tilapia. By replacing up to a third of the fishmeal with algae-meal, the scientists were able to maintain "fish growth, feed conversion, and survival similar to the reference diet," or a traditional aquafeed diet rich in fishmeal or fish oils.
"The possibilities for developing a sustainable approach to aquaculture are exciting," said the project's lead scientist, Dartmouth Assistant Professor Pallab Sarker in an interview for the online publication New Atlas. "Our society has an opportunity to shift aquafeed's reliance on fish-based ingredients to a fish-free product that is based on marine microalgae, and our findings provide new insight into how we can get there."
How Algae-based Feed May Improve Aquaculture
Fish raised through traditional fish farming methods are generally fed a diet of feed that includes fishmeal and fish oil. Aquaculture opponents often cite that aquafeed manufacturing requires nearly 70 percent of the world's fishmeal and fish oil, which is obtained from small, ocean-caught fish including sardines, menhaden, anchovies, herring, and mackerel. These smaller fish are critical to the marine food chain. Currently, 25 percent of the world's commercially caught fish is used for fishmeal production. If a new substitute for aquafeed could be developed, it would prove to be a game changer for aquaculture.
For a deeper dive into the Dartmouth research, check out the study published by the Dartmouth team in PLOS ONE.