快猫短视频

ONE of the world鈥檚 most valuable fish could be driven to extinction because an international conservation body has miscalculated how many are left in the wild. So claim fisheries scientists who are warning that flawed science is behind a decision this month to allow continued fishing of beluga sturgeon, whose caviar can fetch $3000 a kilogram.

Trade in beluga and the caviar they produce is governed by the Convention on International Trade in Endangered Species. CITES believes that beluga sturgeon numbers are on the increase, reaching 11.6 million last year, up from 9.3 million in 2001 and 7.6 million in 1998. Based on those estimates, it has sanctioned Russia, Iran and other nations bordering the Caspian Sea, the fish鈥檚 last surviving stronghold, to harvest up to 155 tonnes of beluga sturgeon and export up to 9 tonnes of caviar.

But critics say there may in fact be fewer than half a million fish left, and that raw data published by CITES itself suggests that the sturgeon population crashed by 40 per cent in 2002 alone. Continued fishing and trade in beluga caviar will only hasten the demise of the species, they say. CITES鈥檚 approval also comes at a time when the US government, the world鈥檚 leading importer of beluga caviar, is considering an outright ban.

CITES is standing by its assessment of sturgeon stocks. Following a crackdown on poaching by the Russian mafia, 鈥渢he historical decline has been arrested, and populations have increased鈥�, claims deputy director-general Jim Armstrong. Countries bordering the Caspian Sea 鈥渁re truly starting to turn the situation around鈥�, he says.

CITES bases its assessment of beluga sturgeon numbers on statistics produced by the Caspian Fisheries Research Institute in Astrakhan, Russia鈥檚 caviar capital. Russian researchers estimate beluga populations based on small survey trawls carried out each summer. Last year鈥檚 figure of 11.6 million fish is based on a total research catch of just 56 beluga. The Russian calculation assumes that for many of the trawls, either 24 fish, or 10 fish, escape the path of the trawl for every one caught in the net. The difference depends on the size of trawling net used.

But Ellen Pikitch of the Wildlife Conservation Society in Washington DC, which is pushing for a ban on beluga caviar, claims that standard models used by UN and US fish researchers usually assume that at most one fish gets away for every one caught. Apply that formula and the real beluga population could be less than half a million. If so, the rate of capture sanctioned by CITES means that 鈥渧irtually all mature beluga sturgeon will fall prey to either legal or illegal fishing, leaving the population at greater risk of extinction鈥�, Pikitch says.

Armstrong says the validity of the demographic model used by CITES is justified by a scientific review written by Russian researchers. But a copy seen by 快猫短视频 admits that 鈥渄ata on sturgeon catchability is very contradictory鈥� and 鈥渟cientists do not agree鈥�. The review also fails to cite any reference later than 1991.

Pikitch says raw survey data published by CITES shows that the number of beluga caught in each survey trawl went down by 39 per cent last year, and the number of adult beluga appearing in rivers for spawning also fell. This contradicts CITES鈥� estimates of rising numbers, she says. 鈥淐ITES is using unreliable data without any review by independent experts,鈥� agrees Vadim Birstein, a Russian sturgeon geneticist based in the US. 鈥淚t is expecting us to believe they have performed a miracle.鈥�

CITES鈥檚 optimism rests mainly on the belief that poaching, which once caught 10 times as many beluga as legal fishing, has been contained. A crackdown has 鈥渃ompletely closed the illegal international trade鈥�, Armstrong says. But according to the Russian press, the police chief in Astrakhan has reported a 20 per cent increase in sturgeon poaching this year.

Beluga are also threatened by toxins in the Caspian Sea, where 80 to 90 per cent of the world鈥檚 sturgeon catch is taken. According to research published this summer, levels of DDT and PCBs in beluga are higher than in other sturgeon, and are sufficient to damage reproduction (Marine Pollution Bulletin, vol 46, p 741).

Behind the disagreement lies a difficult conservation dilemma, however. Beluga, like other Caspian Sea sturgeon, are largely cut off from their natural river spawning grounds by dams. Armstrong says around 90 per cent of beluga now come from artificial hatcheries, which are very expensive to build and maintain. So perversely, a total ban in international trade would stop the money that pays for the hatcheries, and might itself lead to the species鈥� extinction, he says.