Soviet industrial practice and disregard for the external effects of an aggressive market economy have significantly jeopardized the lives of plants and animals in and around the Caspian Sea. The steep decline in fish resources due to over fishing, pollution and other human-related factors, such as the introduction of alien species, is destroying the balance of ecosystems and threatening several of species.
With the opening of the Volga-Don canal in 1952 navigation between the oceans and the Caspian became possible. Contact between the previously secluded Caspian marine ecosystem and the outside world was consequently inevitable.
The connection led to the introduction of various alien species (plants and animals not native to the habitat). The most threatening event for the Caspian ecosystem was the arrival of the North American comb jelly (Mnemiopsis leidyi). It was brought accidentally to the Caspian in the ballast water of oil tankers. A voracious feeder on zooplankton and fish larvae, it first arrived in the Black Sea in the early 1980s where it changed the whole ecosystem and contributed to the collapse of more than two dozen major fishing grounds. From there the comb jelly also invaded the Azov, Marmara and Aegean Seas and most recently the Caspian.
The comb jelly is well adapted to the habitat (salinity, temperature, and food range) and reproduces faster than endemic species. As it eats the same food as them, it has had a drastic effect on their numbers, upsetting the entire food chain. The commercial fishing industry is afraid of losing the kilka, (g. Clupeonella) and other valuable catches, with consequent effects on human livelihoods and food sources for the Caspian seal and sturgeon population (Huso huso). Studies show that between 1998 and 2001, kilka catches by Iranian fishermen dropped by almost 50%, representing a loss of at least $20m per year.
Combating the intruder is a delicate task. Introducing another foreign species, a natural enemy of the newcomer, might just postpone or redirect the problem. However experience from other parts of the world shows that foreign species have not always been successful in the long run, although a few have durably conquered the new environment.
Caspian seals fight for survival
The Caspian seal (Phoca caspica) population has decreased dramatically in recent years. Several factors have contributed to this alarming trend. A virus killed large numbers of seals. Although no direct link has been proved between the virus and environmental pollution, it may be assumed that the high concentrations of DDT and heavy metals measured in the seals weakened the animals’ natural resistance. Moreover kilka, the seals’ main source of nutrition, have been decimated by the comb jelly, further aggravating the seals’ predicament. Intensive navigation, poaching with the pretence of scientific research, fluctuations in sea level and climatic changes are also contributing to the drop in the seal population and threatening their survival. Higher winter temperatures, possibly related to changes in global climate observed in recent years, have caused thinner ice coverage and restricted the traditional reproduction grounds in the shallow waters of the northern Caspian. Recent research by the Caspian Environment Programme estimates the number of living seals to be as low as 110,000. A further reduction in ice cover could well be one of the major threats facing the Caspian seal in the future.
Catching the last sturgeon
The Caspian area is the world’s main producer of wild caviar (83% in 2003) and supplies the three largest markets, the European Union, Japan and the United States. The construction of several hydroelectric power plants and dams along the Volga river significantly altered the flow of water into the delta and destroyed about 90% of the sturgeon’s spawning grounds, which can be as far as several hundreds of kilometres upstream. With high levels of water pollution, sturgeon also suffer from various diseases. According to the survey of the Food and Agriculture Organization, reported data from Caspian states excluding Iran indicate that the sturgeon catch has dropped from an average of about 22,000 tonnes a year in the 1970s to about 1,500 tonnes a year since 2002.
Pressure from the international community having raised awareness of its value as a bio-resource, the region is now struggling to save the sturgeon. To protect the vulnerable fish species more then 100 million sturgeon and bony fish juveniles have been released into the Caspian in recent years. Four years ago Azerbaijan, Kazakhstan and Russia agreed to restrict further export of commercial fish stocks. All three countries, as well as Iran, are party to the UN Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). According to official information received by the CITES secretariat, the temporary ban on caviar trade issued in 2001 has prompted a set of measures lifting the immediate risk of extinction. The caviar trade reportedly fell by about 70% between 1999 and 2003 but there is still every reason to monitor development of the sturgeon population and keep it on the list of endangered species. However it is not clear to what extent the temporary ban on caviar exports has boosted well established illegal domestic and international trafficking, obviously not accounted for in the official figures. To combat the illegal trade in caviar, governments around the world have agreed to a universal caviar labelling system to inform traders and consumers.