The United Nations on Monday lifted a ban on exports of beluga caviar, the most expensive type of the delicacy, after Caspian Sea states agreed to limit catches in view of concerns over declining fish stocks. But a leading environmentalist group called the decision "irresponsible" because the beluga sturgeon was on the brink of extinction, while another urged consumers to boycott the caviar.The U.N. Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) ended a one-year freeze on other exports of caviar last month despite environmentalists' concerns about falling sturgeon populations.Producers of beluga caviar -- a luxury food item which can cost up to 600 euros per 100 grams ($220 per ounce) -- were given a month to provide information on stocks of beluga sturgeon, which the World Conservation Union regards as a species under threat.Caspian neighbors Azerbaijan,Iran, Kazakhstan, Russia and Turkmenistan had agreed to a combined export quota of 3,761 kg (8,292 lb) of beluga caviar for 2007, 29 percent lower than the last limit in 2005, CITES said in a statement.Willem Wijnstekers, secretary-general of the Geneva-based environmental body, said the small quota should help reduce the depletion of sturgeon from the Caspian Sea, the source of more than 90 percent of the world's caviar.But environmentalists attacked the decision to re-open trade in the most valuable caviar, saying overfishing, poaching, pollution and poor management had cut the Caspian beluga sturgeon population by 45 percent between 2004 and 2005."This is irresponsible behavior by international trade officials," said Ellen Pikitch, executive director of the Pew Institute for Ocean Science and co-founder of Caviar Emptor, a group campaigning to protect Caspian Sea sturgeon."With beluga sturgeon, we have a species on the brink of extinction that has lost more than 90 percent of its population in recent years. It's a death sentence to allow trade of its precious eggs to resume," she said.Dawn Martin, head of the advocacy group SeaWeb, called on buyers to boycott wild Caspian Sea caviar in favor of farmed caviar produced in the United States and Europe."It is now up to consumers to help save the sturgeon from extinction by not eating the eggs of an endangered species," Martin said.In a statement issued after the CITES announcement, Caviar Emptor said it believed the U.N. body should require Caspian countries to agree to "a scientifically valid sturgeon recovery plan" as a precondition for future caviar export quotas.