Vital Caspian Graphics 2

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 per cent, representing a loss of at least $20 million per year.

In 2003-06, a small decrease and stabilisation of jelly biomass was observed. However, in some areas huge blooms still occur, as recorded in summer 2005. 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.There is currently no agreement on the deliberate introduction of another foreign species.

Mean sea surface temperature

Winter

Summer

Comb jelly ( Mnemiopsis leidyi) is spreading in the European seas

B A R E N T S S E A

Altitudes in metres

1 000 2 000 3 000

WHITE SEA

NORWEGIAN SEA

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Volga

NORTH SEA

Area of spread of the comb jelly Mnemiopsis leidyi

BALTIC SEA

ARAL SEA

Volga

ATLANTIC OCEAN

Don

ENGLISH CHANNEL

Volga

Don

SEA CASPIAN

B L A C K S E A

ADRIATIC SEA

1

2

3 4

5

6

7

8 9

10

21 22 23 24 25 26

27 28

AEGAN SEA

Mean summer sea surface temperature (°C) Sources: After Kosarev and Yablonska, 1994 and Dumont 1998 in Fabienne Marret, Suzanne Leroy, FranНoise ChaliО, FranНoise Gasse, “New organic-walled dinoflagellate cvysts from recent sediments of Central Asian seas”, Review of Palaeobotany and Palynology 129 , 2004; N.V. Aladin, Y.S.Chikov, V.E. Panov and I.S. Plotnikov, Chronology of Mnemiopsis and Beroe invasions to the Black, Azov and Caspian Seas, Presentation to the HELCOM-BSRP Meeting on Ballast Waters, Klaipada-Palanga, February 2005. Mean winter sea surface temperature (°C)

Source: Daisie database, accessed in September 2011; adapted from Panov, 2008; base map by Philippe Rekacewicz.

M E D I T E R R A N E A N S E A

0

1 000 km

500

60

61