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Ecosystems paying the price
With the opening of the Volga-Don canal in 1952 navigation between the oceans
and the Caspian became possible. Contact between the previously secluded Cas-
pian 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
ecosystemwas 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. Clu-
peonella
) and other valuable catches, with consequent effects on human liveli-
hoods and food sources for the Caspian seal and sturgeon population (
Huso
huso
). Studies show that between 1998 and 2001, kilka catches by Iranian fish-
ermen dropped by almost 50%, representing a loss of at least $20m per year.
Combating the intruder is a delicate task. Introducing another foreign spe-
cies, a natural enemy of the newcomer, might just postpone or redirect the
problem. However experience from other parts of the world shows that for-
eign species have not always been successful in the long run, although a few
have durably conquered the new environment.
Soviet industrial practice and disregard for the external effects
of an aggressive market economy have significantly jeopard-
ized the lives of plants and animals in and around the Caspian
Sea. The steep decline in fish resources due to over fishing, pol-
lution and other human-related factors, such as the introduc-
tion of alien species, is destroying the balance of ecosystems
and threatening several of species.
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