MONTREAL--The Caspian Sea was once a thriving ecosystem, teaming with seals and enormous sturgeon. But life has become close to untenable for these species from years of overharvesting and habitat loss, combined with pollution and invasive species. At a joint meeting here of the Ecological Society of America and the International Association for Ecology, researchers described more grim news about the sturgeon, called for aggressive conservation measures, and presented the first scientific survey of the Caspian seal population.
The number of beluga sturgeon (Huso huso)--the species most harvested for caviar--has plummeted by more than 90% since 1960. At a workshop at the meeting, scientists reported that no wild, reproducing Beluga females have been found this year in Kazakhstan, which means there won't be any eggs from which to raise hatchery fish; another worrisome indicator is that black market caviar was unavailable in some places. And because the fish take an average of 15 years to mature, their recovery faces an uphill battle.
"Other sturgeon are following in the footsteps of beluga," said Ellen Pikitch, director of the University of Miami's Pew Institute for Ocean Science. The stellate sturgeon has taken a particularly astonishing fall over the past 13 years: The number of spawning fish entering the Volga river, which flows into the Caspian, plummeted from 322,000 to 24,000 between 1993 and 2000. The only exception to the trend has been the Persian sturgeon, which is being boosted by hatcheries in Iran. The consensus of the group was that the conservation status of the Beluga should be raised to critically endangered, and that countries should ban all lethal captures.
Also at the meeting, Susan Wilson of the Tara Seal Research Centre in Northern Ireland and working with the Institute of Zoology in London, U.K., reported new data on Caspian seals, which have high levels of DDT and other pollutants and have suffered from epidemics of canine distemper virus. In 2000 and 2001, some 10,000 seals are thought to have died from various causes.
To get a better handle on how big a loss this represents, a team led by Tero Harkonen of the Swedish Museum of Natural History, Stockholm, in February conducted an aerial survey of the ice field on which the seals overwinter. The researchers estimate that the population is 111,000--about 25% of the number used by Caspian countries to set hunting quotas. Wilson noted the seal's dramatic decline--83% over the past 50 years, according to previous population models--is steep enough to qualify it for endangered status under World Conservation Union guidelines.
More on the species of the Caspian Sea