Caspian Sea 2011
European Pikeperch is an active predator, pre- ferring freshwater. Catches dropped from 55 thou- sand tonnes in 1948 to 0.77 thousand tonnes in 1979. In subsequent years, catches increased a lit- tle, but stayed at the low level of a few thousand tonnes. Marine pikeperch ( Sander marinus ) was fished from the 1930s to the 1950s, but is now very rare and even included in the Red Data Books. Wels catfish ( Silurus glanis ) and northern pike ( Esox luceus ) are other predator species. Both were never considered as important commercial spe- cies, although their combined catch reached up to 24 thousand tonnes in 1956. Catches of both spe- cies have decreased, although they are more sta- ble than those of other fish species. Present-day catch levels are about 4 to 5 thousand tonnes for pike and 6 to 8 thousand tonnes for wels catfish. Mullets ( Liza aurata & Lisa saliens ) were intro- duced into the Caspian Sea in the early 1930s and appeared in the commercial fishing statis- tics from 1950 onwards. Both mullet species are fished mainly in the south Caspian. Fishing has been intensified over the last decade by Iran. The reasons for fluctuations in catches are unknown. Seal population reduction The seal is the only marine mammal in the Caspian Sea, feeding on tulka and other small fish. It is an endemic species in the Caspian and, because of this, is considered vulnerable. During its life span, the Caspian seal migrates from the frozen North Caspian in winter to the South Caspian in summer, and then returns to the north to give birth to pups on the ice. Dur- ing these migrations, the Caspian seal can be found in all locations in the sea. It is unclear how many seals remain in the Cas- pian Sea. From a population estimated at more than one million in the early years of the twen- tieth century, population estimates now vary be- tween 110 000 and 350 000. For more than 100 years, hunting of seal pups was carried out in the frozen North Caspian area each winter. In the early twentieth century, nearly 100 000 seals were
hunted each year; later a quota was set at 40,000 pups per year, further reduced to 20,000 pups per year. The hunting quota, set by the Caspian Bioresources Commission for 2007, was 18,000 seals. Even if during the last decade, no organized hunting has taken place in the North Caspian, the hunting quotas exceeded the estimated annual pup production (Härkönen et al 2008). Recent mass mortalities have reduced the seal population even further. In 2000, a mass mortality due to the canine distemper virus (CDV) caused tens of thousands of deaths throughout the Cas- pian (Azerbaijan, Kazakhstan, Russia, and Turk- menistan). Pollution has been shown to result in a high number of barren females (up to 70% of fe- males are thought to be barren) which also threat- ens the overall seal population. Besides pollution and hunting, other stress factors impact on the Caspian seal population. A major food source for the seals is the small tulka fish, once abundant in the Caspian. Another factor which has become apparent in recent years is intrusion on to the ice
Historical decline of the Caspian seal ( Pusa caspica )
160 Thousands of seals hunted
1950 1960 1970 1980 1990 2000 0
Source: Caspian Environment Programme, Transboundary Diagnostic Analysis Revisit, 2007.
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