Geneva ? Illegal sales of caviar in Europe are endangering the survival of some sturgeon species, two conservation groups said.

More than 25,000 pounds of illegal caviar were seized in Europe in the past five years, the World Wildlife Fund and Britain-based TRAFFIC, which monitors trade in wildlife, said in a statement released today. Far more was sold on the street and in fine restaurants, the groups said.

The illegal trade is carried out by culprits ranging from individuals who sell single jars in open-air market stalls to operations that pay couriers to deliver suitcases stuffed with black-market sturgeon roe.

Legal caviar exports are regulated by an international system of permits run by the U.N. Convention on International Trade in Endangered Species of Wild Fauna and Flora. The Geneva-based body imposes annual quotas on caviar exports – some 250,000 pounds in 2004, down from about 320,000 pounds in 2003 – but environmentalists say that hasn’t prevented the sturgeon’s decline.

While the amount of legally traded caviar plummeted by almost 70 percent between 1998 and 2003 – to about 100 tons annually – TRAFFIC and WWF said rising illegal sales were “very likely” offsetting the decline.