Farming Fish No Longer Relies Only on Fish Meal Feeds
The world's farmed fish industry no longer relies entirely on fish meal to feed its most valuable products such as salmon and trout, University of Idaho aquaculture expert says.
A big reason was a doubling of the price of fish meal in 2006, the result of a number of factors including lower catches in Peru associated with an El Nino event.
China's growing economy allowed it to buy up a sixth of the 6-plus million metric tons of fish meal available on the world market each year.
"That changed everything," said Ronald Hardy, who directs the university's Aquaculture Research Institute at Hagerman, Idaho, the epicenter of U.S. farmed rainbow trout production.
Hardy moderated a panel Friday during the American Association for the Advancement of Science annual meeting in San Francisco about advances in sustainable seafood production.
The world's largest general scientific conference is expected to draw as many as 10,000 participants. This year's theme is "Science and Technology for Sustainable Well-Being." In addition to Hardy, University of Idaho researchers Jack Brown and Jon Van Gerpen will present a display and program, "Biodiesel: Field to Fuel," during Family Science Days Feb. 17 and 18.
Hardy spoke about advances in reducing fish farming's reliance on fish meal and fish oil. He said prices surged from the $700-a-ton high he'd seen during his 30-year career to a crest of $1,400 a ton in 2006.
"High prices for fish meal are here to stay, making alternatives such as soy protein concentrate and wheat gluten affordable alternatives," Hardy said. In addition, higher prices for fish meal will stimulate innovative approaches to recovering protein from seafood processing by-products, much of which is currently discarded.
Supplying 45 percent of the world's fish supply in 2006, aquaculture must find ways to grow beyond fish meal and oil supplies to feed a growing population's appetite, he added.
Decades of research have shown that proteins derived from grains such as corn, wheat and barley can to provide the protein-rich ingredients needed in feeds for farmed salmon and trout.
Growing ethanol production, particularly the use of corn to make the alcohol-based fuel, could be a boon to some types of fish farming. Dried distillers grains contain the 28 to 30 percent protein that fish like tilapia and catfish require.
Trout and salmon need 40 percent protein in their diets and that, too, can be met by ethanol producers, Hardy said. Producing the high-protein byproduct, however, will mean turning existing processes upside down.
Ethanol producers now ferment the whole corn kernel, which reduces the amount of protein in the by-products below the needs of trout and salmon.
Focusing on first removing the byproducts, protein and oil, then fermenting the remaining starch for fuel, yields a high-quality and valuable fish feed, Hardy said. About 10 percent of ethanol plants in the U.S. now use that process.
Protein concentrates produced from soybeans, wheat, barley and canola also can supplement fish feeds to offset fish meal, especially if they are combined. Each of these protein concentrates is deficient in an essential amino acid, but combining them offsets the nutritional deficiencies to some degree.
Much of the work on plant protein-based feeds have concentrated on reducing phosphorus concentrations to protect water quality.
Research in Idaho helped lead the way because its concentration of trout farms that produce nearly three-fourths of the trout headed for the nation's tables. In the 1990s, water quality in the Snake River suffered from an overload of phosphorus from a host of sources, fish farms among them.
Reducing phosphorus in trout farm effluents and periodic lack of fish meal fed interest in grain-based fish feeds, Hardy said, and led to increasing use of alternatives available now.
Harder to replace will be fish oil. People eat fish in part because it contains Omega-3 fatty acids, which are recognized as an essential component of a healthy diet.
Fish fed corn oil or soy oil, however, resemble the plant's chemical profile more than a fish, Hardy said. New research is exploring phased, rather than constant, doses of fish oil to maintain the healthy oil profile of farmed fishes.
Recent developments in the definition of organic and sustainable fisheries from Great Britain promise to help out there, too.
Fish trimmings, or processing scraps, from sustainable fisheries can be used to produce marine protein and oil, potentially yielding up to 20 percent of the world supply, Hardy said.
"Alaska has two internationally certified sustainable fisheries, the pollock and salmon fisheries," Hardy said. "Processing by-products are a promising source of sustainable marine protein and oil for the growing aquaculture industry."
In the past, the cost of converting the seafood processing by-products to meal or oil in Alaska was too high to produce cost-effective products until the uptick in fish meal prices, Hardy said.
