Success Story

Fish Story Has Happy Ending for American Aquaculture and Consumers

ars fish story

Developing a new formula for rainbow trout food might not, at first glance, seem like a high-profile project. But for a federal laboratory in Hagerman, Idaho, it led to a breakthrough with far-reaching implications for America's commercial fish industry, and for food supplies in the developing world.

Researchers at a USDA Agricultural Research Service (ARS) lab, working with a commercial partner, demonstrated that rainbow trout can be grown more successfully on a plant-based diet than a conventional fishmeal diet. This is significant because the current practice of feeding fishmeal to farm-grown fish is not sustainable, supplies of the marine species used for fishmeal, such as anchovy, menhaden and herring, cannot keep pace with rapidly growing demand.

Drs. Ken Overturf and Rick Barrows of the Small Grains and Potato Germplasm Research Unit not only developed a successful grain-based food formula, but also cross-bred trout to produce fish that actually grow better with the plant-based formula.

"We were coming at it from both sides," said Overturf, a research geneticist.

Those new strains of trout, grown by the commercial partner, Clear Springs Foods of Buhl, Idaho, are already reaching tables in American homes and restaurants. They account for 18 percent of all commercially grown rainbow trout in the U.S.

More than half of the fish consumed in the U.S. now comes from commercial aquaculture. In addition to trout, popular species include Atlantic salmon, sablefish, catfish, tuna and cobia. While the lab's research focused only on trout, the findings hold promise for commercial farmers of other species as well. Plant-based food, and new strains of fish that thrive on it, will help support the growth of commercial aquaculture in the U.S and keep fish a key component of the American diet.

These innovations will also benefit many developing countries, where farm-grown fish supply the only source of protein to much of the local population. Currently, said Overturf, most fish farmers in these countries use poor-quality feeds. But with better feeds and improved fish strains, production would increase dramatically.

Overturf and Barrows have been developing the plant-based fish feed and the new strains of rainbow trout in the Hagerman lab for 11 years. In 2006, the ARS entered into a Cooperative Research and Development Agreement (CRADA) with Clear Springs, the largest trout producer in the world, to test the plant-based feed and the new trout strains in a commercial environment. A second CRADA with Clear Springs was signed in 2011 to continue the research.

In the early phases of his research, Overturf determined that some individual rainbow trout families were better able than others to process plant-based feed. By cross-breeding trout with those qualities for four generations over 10 years, he produced fish that gain weight quicker than standard commercial trout on fishmeal-based diets, an improvement that makes the new strains of fish attractive to farmers.

Essentially, said Overturf, "We changed the physiology of the fish to extract and utilize nutrients more efficiently." The new strains of fish also appear to have a firmer muscle texture. And, he said, they taste "fabulous." In fact, the lab conducted a blind taste test for fish farmers, and found that they couldn't tell the difference between the plant-fed and fishmeal-fed trout.

The lab's plant-based trout diet, in the form of pellets, is being produced commercially by several companies with proprietary formulas. Because the grains used in the feed do not contain Omega-3 fatty acids, a valuable dietary benefit of eating fish, current formulas include fish oil to make up for that deficiency. However, since the fish oil comes from the same marine species as the fishmeal, and those supplies are limited, the lab is now working to breed trout that can convert oil from algae and soy into Omega-3 fatty acids.

As a result of the lab's successful work with the rainbow trout, it was awarded the "Outstanding Commercial Success" award by the FLC Far West Region.