Aquaculture will reach a landmark 50 percent of all human consumption of fish this year, a new scientific study predicts.
Although more efficient than ever, the aquaculture industry still puts a heavy strain on global fish stocks by demanding huge harvests of wild fish to provide feed for the fish farms, the study, published in the Proceedings of the National Academy of Sciences (PNAS) web edition, shows.
“The huge expansion is being driven by demand,” said lead author Rosamond L. Naylor, a professor of environmental Earth system science at Stanford University and director of the Stanford Program on Food Security and the Environment.
Consumer demand for long-chain omega-3 fatty acids has increased sharply, and global aquaculture has almost tripled between 1995 and 2007. Oily fish, such as salmon, are a major source of these omega-3s, which are effective in reducing the risk of cardiovascular disease, according to the US National Institutes of Health.
“As long as we are a health-conscious population trying to get our most healthy oils from fish, we are going to be demanding more of aquaculture and putting a lot of pressure on marine fisheries to meet that need”, professor Naylor added.
From an environmental perspective, one problem with aquaculture is the huge amount of fishmeal and fish oil the farms use to maximise growth and flavour. Those products come from less valuable wild-caught species, such as anchoveta and sardine.
Consequently, aquaculture’s share of global fishmeal and fish oil consumption more than doubled over the past decade to 68 percent and 88 percent, respectively,” the study shows. Currently, it may take as much as 5 pounds of wild fish to produce 1 pound of salmon.
One way to improve the situation, the scientists say, would be to lower the content of fish oil in the farmed salmons’ diet. Reducing the content of fishmeal would have much less effect.
Naylor and her co-authors also point out that several fish-feed substitutes are currently being investigated, including protein made from grain and livestock byproducts.