Farmed Trout Go Vegetarian (Sort Of), Taste Virtually The Same
By Tom Banse
The search is on for a cost-effective alternative fish food. And we don't mean the Ben & Jerry's Ice Cream flavor. What we're talking about is the pellets fed to farmed fish. A key ingredient in commercial feed is other fish caught in the wild. Northwest trout farmers - and some salmon growers - recognize that practice is unsustainable. But trout are carnivores. They can't just become vegetarians, or can they?
Correspondent Tom Banse joined a taste test to see if seafood consumers can tell any difference. He was greeted by coordinators at the School of Food and Science at Washington State University in Pullman.
"Hello. Welcome to the trout fillet tasting panel. Here's some water and crackers to rinse your palate..."
Banse is one of 72 volunteers recruited as taste testers.
"Here's your first sample. Just push the button when you're ready for your next sample. Follow the directions on the screen, okay?"
"Alright, so if it's true that you are what you eat, I should be able to tell the difference between these trout samples that I'm being presented because one was raised on fish meal, another on animal proteins and a third on a mostly vegetarian diet," Tom says.
Tom tries sample A: "Pretty classic trout flavor there. These have been poached. There's no sauce on them. So you get pure, unadulterated trout. I couldn't really tell you if that was raised on fish, land animals... or vegetables."
Researchers at the WSU School of Food Science prepare trout samples. Photo by Tom Banse
He compares notes later with some of his fellow testers. Some got a little bit of "grassy" flavor from what turned out to be the vegetarian-fed trout fillet. The trout raised on traditional fish meal had slightly more "fishy" flavor and aroma. The trout that ate chicken byproducts did not taste like chicken.
The definition of success in this aquaculture experiment would be for the non-fish alternative diets to work out more or less the same as the current fish-based feed. Professor Carolyn Ross supervises the taste testing. She's been serving panelists trout raised on different feeds since 2008.
"I think they are getting close. Certainly, there are differences between samples. But whether that is a game changer or not is a different question. So yes, I can tell one has a more fishy aroma. I can tell one is firmer. But if you're if you're sitting down at home having a BBQ, it's not going to make a big difference," Carolyn Ross says.
Idaho is by far the number one trout producing state in the nation. A longtime fish grower there says finding a cost-effective alternative feed is the industry's "number one" priority. Leo Ray of Buhl, Idaho says fish meal used to cost around $300 per ton about 15 years ago. Nowadays, the same amount runs him close to $2,000.
"We knew this was coming. There is a limit on the amount of fish meal the ocean can produce and we've hit that limit," Ray says.
Ray says the suppliers he buys from have already reduced the wild fish content in commercial feeds somewhat. He and his competitors in southern Idaho have tested all sorts of alternative diets. They've fed their fish poultry byproducts, corn and soybean protein, coconut oil, and ground up insect larvae to name a few. Ray doubts going completely vegetarian is the answer.
"We have healthier fish if we put a little bit of fish meal in the diet. I think what we will end up with is a diet that instead of using 20 or 30 percent fish meal, will be using 5% fish meal," Ray says.
University of Idaho Extension educator Gary Fornshell says an upcoming economic analysis could shed more light on what the ultimate formulation of trout feed will be. Federal government and university researchers are scheduled to present their findings to an industry gathering in Twin Falls on June 8th. There, fish farmers will get their own chance to nibble the various trout fillets we sampled for you.
Photo: Alternative feeds resulted in slightly different colors and textures in trout fillets. Photo by Tom Banse
U.S. Fish and Wildlife Service scientist Wendy Sealey leads the multi-agency study of trout dietary treatments. She is based at the Bozeman Fish Technology Center. "It goes beyond trout," Sealey says. "It applies to other aquaculture species."
Parallel studies are testing alternative feeds for farmed Atlantic salmon and several species of warm water fish.
"Salmon are harder to wean off fish meal," said Ray, while tilapia could fairly easily be converted to a plant-based diet.