Once considered to be a fledgling industry not so long ago, "Aquaculture is set to reach a landmark in 2009, supplying half of the total fish and shellfish for human consumption," the authors wrote.
Way back when, 20 or so years ago, I entered the field of aquaculture after witnessing first hand the ever increasing year to year decline in the traditional fishing industry. Back then we all felt to be on the verge of something new and big, today we can look back and see just how far the industry has come. The growth has been tremendous but it has certainly not been without challenges.
The report states that between 1995 and 2007, global production of farmed fish nearly tripled in volume, in part because of rising consumer demand for long-chain omega-3 fatty acids. 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 National Institutes of Health.
This growth has placed ever increasing pressure on marine resources due to the need for large amounts of feed made from wild fish harvested from the sea. "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. "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." Sourcing sustainable feed ingredients is one of the largest challenges faced by the industry today.
One way to make salmon farming more environmentally sustainable is to simply lower the amount of fish oil in the salmons diet. According to the authors, a mere 4 percent reduction in fish oil would significantly reduce the amount of wild fish needed to produce 1 pound of salmon from 5 pounds to just 3.9 pounds. In contrast, reducing fishmeal use by 4 percent would have very little environmental impact, they said.
"Reducing the amount of fish oil in the salmons diet definitely gets you a lot more bang for the buck than reducing the amount of fishmeal," Naylor said. "Our thirst for long-chain omega-3 oils will continue to put a lot of strain on marine ecosystems, unless we develop commercially viable alternatives soon."
Naylor and her co-authors pointed to several fish-feed substitutes currently being investigated, including protein made from grain and livestock byproducts, and long-chain omega-3 oils extracted from single-cell microorganisms and genetically modified land plants. "With appropriate economic and regulatory incentives, the transition toward alternative feedstuffs could accelerate, paving the way for a consensus that aquaculture is aiding the ocean, not depleting it," the authors wrote.
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