The suspension, called for by the secretariat of the Convention on International Trade in Endangered Species, was described as a temporary measure to compel nations that still export caviar and other products from wild sturgeon to demonstrate that their fishing practices are not pushing the remaining fish populations toward extinction.

Exporting nations must "ensure that the exploitation of sturgeon stocks is commercially and environmentally sustainable over the long term," said Willem Wijnstekers, the convention's secretary general.

The suspension also bars signatory nations from importing sturgeon products. This means that Western retailers would still be able to sell wild foreign caviar they have already imported. But once that inventory is depleted, consumers would most likely have to purchase farmed eggs, which are generally regarded as less desirable, or eggs from limited domestic supplies. In any event, the market would tighten.

Sturgeon - primeval, long-lived and sometimes massive - are the vestiges of an ancient line of fish. Their eggs and meat, and the trade that surrounds them, have become deeply entwined in the histories, cultures and economies of the regions that produce them. Sturgeon products, legal and illegal, are thought to be worth at least several hundred million dollars each year, and perhaps much more.

But the remaining sturgeon fisheries have all suffered from plummeting populations, caused by dams that block spawning routes, pollution, excessive fishing, corruption and highly organized black markets. And as a luxury item in the West and among the newly rich in the post-Soviet states, the fish and their eggs have become more valuable as they have become more rare.

Caviar from beluga sturgeon, the most prized species, fetches more than $200 an ounce, roughly double the price of a year ago.

Scientists and managers have noted that even before prices soared, there had been several local extinctions of sturgeon, and many species, including some in the United States, had been reduced to marginal populations. Moreover, the remaining commercial stocks are the last reserves, a condition that lent urgency to the secretariat's demand for more thorough management plans. "We just have to get this right, because there are not enough fish left," said David Morgan, head of the secretariat's science unit.

The suspension covers all principal areas that export wild sturgeon meat or eggs, including the Caspian Sea, where 90 percent of the remaining trade originates; the Amur River, on the Russian-Chinese border; the Black Sea and the lower Danube.

It applies to 10 nations that still actively export products: Azerbaijan, Bulgaria, China, Iran, Kazakhstan, Romania, Russia, Serbia and Montenegro, Turkmenistan and Ukraine, the secretariat said. The convention covers exports only, meaning fish caught in each country can still be sold on domestic markets.

But the main importing nations - among them the United States, Britain, France, Germany and Switzerland - are all parties to the 169-nation convention and are expected to follow the secretariat's call to block imports.

Susan Lieberman, director of the World Wildlife Fund's global species programs, said she expected the United States, which in 2005 unilaterally banned the importation of beluga sturgeon products under the Endangered Species Act, to accept the new rules.

The United States Fish and Wildlife Service, which is charged with enforcing the convention in the United States, did not publicly comment on the secretariat's announcement.

There was little immediate reaction from exporters.

Russia, which trades heavily in sturgeon products for domestic and foreign markets, is on official holiday for New Year and Orthodox Christmas celebrations. Its natural resource officials could not be reached.