Food and Drug administration lab tests have found no detectable levels of melamine in farmed fish from Washington state.
The FDA report follows a scare over melamine-contaminated pet food that was blamed for causing the deaths of an unknown number of dogs and cats in the United States.
The earlier fears over contaminated feed are resurfacing concerns over aquaculture. Fish farms have struggled to improve their own image amid concerns about pollution and complaints about the flavor of the products they produce.
On harvest day at American Gold Seafood company in Puget Sound, thousands of fat Atlantic salmon are sucked up and sent flopping down plastic chutes, where they're funneled into a machine that delivers a pneumatic whack on the head, and a blade to the heart.
The manager, Rob Miller, is proud of this operation.
"These fish are stunned, bled and chilled in two hours, and (then) they're at the processing plant," explained Rob Miller, the plant's manager. "Within 12 hours we can have fresh filets ready to go."
Farmed salmon is cheap, and it's what most Americans eat. But it's also controversial: environmentalists don't like the pollution from the pens, and organic-minded consumers turn up their noses at what they perceive as an inferior flavor. So companies such as American Gold have been trying to develop something they call "natural" farmed salmon.
The difference, Miller said, is the feed.
"In the natural feed there is no land animal protein. So all the protein sources come from either vegetable or fish," he said.
Miller said the theory is that since wild salmon eat fish, farmed salmon should eat feed made from fish. Even so, one of the feed brands used at American Gold may have been contaminated with melamine.
FDA tests show the fish themselves are free of the chemical, but critics of fish farming say the melamine scare should be taken as a warning.
"The important part of this is the feed process, right? Since we're industrializing the whole process of creating fish feed, there's a lot more opportunity for contaminants or problems to enter the system," said Andrea Kavanagh, who directs the National Environmental Trust's "Pure Salmon" campaign.
In principle, Kavanaugh said she doesn't oppose fish farms. They're necessary to relieve pressure on the over-fished oceans, she said.
But she wants government regulations governing the operation of "organic" farmed salmon. Kavanagh is also skeptical of the "natural" label being used to market the fish.
"I think that you can have a better, more sustainable, more environmentally friendly farmed salmon," she said, adding that the farmed salmon on the market is still far from "natural."
Miller readily admits "natural farmed salmon" is a vague concept.
"This is kind of a (fish) diet that we made up. Because there are no criteria for what should be in the 'natural' or 'organic' diets," he said.
As for the purists who refuse to eat farmed salmon, Miller likes to point out that many wild salmon start their lives in Washington state's hatcheries.