OAKLAND, Calif. -- Shawn Mattiuz, manager of the Hapuku Fish Shop in Market Hall, a collection of upscale food purveyors in Oakland's bustling Rockridge district, has been watching the Gulf seafood saga play out in the ice-cooled trays of his display cases.

For a few days after the oil spill turned into a crisis this spring, demand stalled as "everybody freaked out," he said.

Since then, he said concern has died down and he's selling about the same amount of Gulf shrimp as he did pre-spill.

"I get a lot of questions about it, definitely. They want to know if it's regulated," said Mattiuz. "The truth of the matter is from everything that I've read, it's more highly regulated now than it ever has been."

More Gulf waters are reopening to fishermen, and government officials have said seafood cleared for sale has been thoroughly vetted. Whether consumers are buying those assurances -- and the fish -- remains to be seen.

Nationally, an Associated Press-GfK poll that surveyed 1,007 adults nationwide between Aug. 11-16 found that 54 percent did not trust the seafood.

Jimmy Galle, founder of Sausalito-based Gulfish LP and a supplier to Hapuku and a number of upscale restaurants in the San Francisco Bay area and elsewhere, said his business has begun to grow again after a few lean months. "And the shrimp has been nothing less than spectacular lately," he said.

Ann Cashion, co-owner of Johnny's Halfshell in Washington, D.C., one of Galle's clients, sees concerns about Gulf seafood safety fading.

"I find that people aren't even asking right now. It was more on top of people's brains when the oil was still flowing," she said.

Cashion said she thinks the testing is thorough because state officials are involved.

"The state of Louisiana and the Gulf Coast in general has so much to lose if there is any kind of problem with any seafood that gets through inspection, so I know the inspection is going to be thorough and is going to err on the side of 'Let's don't take any chances,' " she said.

Not everyone shares that confidence in Gulf seafood, which accounts for about 2 percent of overall U.S. consumption.

"I would say that I always have a skeptical eye toward government regulation and government certification of things," said Genie Gratto, an Oakland food blogger.

"It's been proven time and time again that, first of all government certification of food is such a massive job, the USDA and the FDA tend to be pretty understaffed in those kind of inspection areas, there's no way they can get everything."

On the other hand, she does have confidence in buying from trusted suppliers, like the small meat and fish market where she shops. She also tries to buy local, which doesn't include Gulf seafood.

The Natural Resources Defense Council and other groups recently asked the Food and Drug Administration and the National Oceanic and Atmospheric Administration to strengthen procedures for determining whether seafood is safe and whether fishing areas should be reopened.

They also want sampling protocols and data published online.

"We're not saying that the seafood is not safe," said Gina Solomon, a senior scientist with NRDC. "We're basically raising questions about the government's procedures, their scientific procedures and their transparency."

One issue is whether government standards are strict enough to protect vulnerable populations, she said. "We want to make sure that the government is setting up a robust seafood safety testing program that will be able to protect the public for years to come, because that's how long this problem is likely to last."

The FDA is reviewing the NRDC letter, but is confident in the protocols, said agency spokeswoman Meghan Scott.

The main issue with oil contamination is potential cancer-causing substances called polycyclic aromatic hydrocarbons, or PAHs. These are pollutants that show up in other foods as well, such as grilled meat.

If there is contamination, fish metabolize it fastest, oysters and crabs slowest and shrimp are somewhere between.

Testing includes "sniffers," who check for traces of oil and lab tests on ground up seafood to check for contaminants.

Because of strict adherence to procedures, the FDA "feels confident in the safety of seafood coming from these waters," Scott said in an e-mail.

"We also understand that we must remain vigilant to ensure the safety of seafood coming from the Gulf. As such, FDA and NOAA will continue to monitor both water and seafood to ensure that tainted fish is not allowed into the marketplace."