HONG KONG — For years, fish sellers in China have labeled something other than salmon as salmon, according to a local media report that outraged sushi lovers across the country.

Now, Chinese fish authorities have responded: That’s perfectly O.K. with them.

Chinese regulators said this week that rainbow trout can be sold as salmon, according to new standards set by a government-affiliated fish association and 13 commercial fisheries. To justify the change in definition, officials cited biology: Salmon and rainbow trout belong to the same fishy family. They also required sellers to note the exact type of fish elsewhere on the label.

Still, the fuzzy definition touched a nerve in a country with a long history of food labeling issues and a vast population of increasingly sophisticated consumers. Thousands took to the internet to blast regulators for lowering food standards instead of fixing the issue. Some declared they would never eat salmon again.

Even patrons at a sushi restaurant said that they could no longer trust salmon enough to eat it raw.