Researchers are working to make aquaculture more sustainable.
"We know that aquaculture is going to be increasingly important for achieving food security around the world. It's the fastest growing food sector, but it's growing in some ways that are unsustainable and raise real problems," Anne Kapuscinski, the Sherman Fairchild Distinguished Professor of Sustainability Science, said, a Dartmouth press release reported.
Many farm-raised fish are regularly fed diets of fish oil and fish meal from anchovies and menhaden. This practice is causing the anchovies and other targeted breeds to be overfished.
"Right now aquaculture is consuming the overwhelming majority of fish meal and fish oil, and unfortunately, they come from marine species that are really healthy and desirable for humans to eat, things like anchovies, herring, mackerel," Kapuscinski said.
A past study by the same researcher concluded that the fishing industry consumes more fish ("in the form of protein and oil from pelagic fishes like mackerel, herring, anchovies, menhaden") than it produces. The result is "a net removal of fish on a global basis."
The researchers believe the industry could be more sustainable if micro-algae was incorporated into the fish's diet.
"People have been increasingly asking, why are we harvesting these fish that people could eat and grinding them up for fish meal and fish oil and putting them into diets to raise other fish, and using up fossil fuel to do this?" Kapuscinski said. "We're trying to find some sustainable substitutes. Micro-algae as a possible substitute are ideal for a species like tilapia that feeds low on the food chain and feeds on algae in nature."
The researchers observed how well tilapia digested three different types of micro-algae and compared it to their digestion of fish products. One type of algae that, was high in omega 3 fatty acids, proved to be a better diet than the commercial option.
The researchers are now studying how much micro-algae can be fed to the fish as a replacement for the popular fish meat diet.
"We're going to evaluate what percent replacement (of micro-algae) still gives good fish growth, good fish survival, and also measure how much it raises the omega 3 fatty acid content of the flesh of the tilapia. Boosting that flesh concentration of the omega 3 fatty acids would make the tilapia even healthier for people to eat," Kapuscinski said.
Including micro-algae into the fish's diet could help reduce ocean pollution.
"The current aquaculture diet produces excessive phosphorous levels in aquaculture effluents," senior Research Associate Pallab Sarker, said."Results of our first experiment suggest that incorporating micro-algae into the diet led to more efficient retention of the diet's phosphorus, and this will also lead to cleaner aquaculture effluents and cleaner water."
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