Caspian Sea 2011
State of the Environment of the Caspian Sea
Bony fish fishing There are about 30 species of bony fish fished commercially in the Caspian Sea. The majority of these are small cyprinids, not included in statis- tics and with only total estimates of catch levels available. The most important bony fish species are Caspian Roach ( Rutilus rutilus caspicus ), Bream ( Abramis brama ), Carp ( Cyprinus carpio ), European Pikeperch ( Sander lucioperca ), Wels or catfish ( Silu- rus glanis ), Northern Pike ( Esox luceus ), and Mullet ( Liza auratus & Lisa saliens ). Caspian Roach was a dominant fish species over a long period of time. They feed in the open sea and return, for a very short period, to low deltas for spawning early in the spring. Its maximum catch was recorded as 167 thousand tonnes in 1935. Roach catches varied over a 20- year period, but the general trend was a decline – from 167 thousand tonnes in 1935; 105 thousand tonnes in 1955; 26 thousand tonnes in 1975; 20 thousand tonnes in 1996; and only 5.7 thousand tonnes in 2008. Within a 70-year time period, catches decreased 30 times. All bream species populate the river deltas and the marine areas around deltas. The dominant species is the European bream ( Abramis brama ). All other bream species ( Ballerus ballerus, Vimba persa, Blicca bjoerkna, Ballerus sapa ) are fished in small amounts and rarely exceed 1 thousand tonnes annually. The maximum catch of Euro- pean bream was more than 100 thousand tonnes in the early 1930s. In subsequent years, the catch level decreased, becoming more or less stable over time at 20 thousand tonnes annually. The lowest catch was recorded in 1979-80, less than 5 thousand tonnes. Carp, like bream, does not usually migrate far into the sea and congregate around del- tas. Carp catches have always been less than bream and roach. The lowest catch levels were recorded in 1982 and 1995 – less than 4 thou- sand tonnes. Over the past ten years, catch levels are believed to have increased, reaching 9.4 thousand tonnes in 2008.
covery period occurred after 1996, culminating in 270 thousand tonnes in 1999. But tulka catches dramatically decreased again in the period 1999 to 2003 in all countries apart from Turkmenistan (with the highest rate of decline recorded in Iran and Russia) (WB 2008). The cause was mass mor- tality of Big-eye and Anchovy tulka in 2001-2002. According to specialists, it happened because of a seaquake, accompanied with release of methane, which results in destruction of biore- sources. The total catch was only 50 thousand tonnes in 2004, while in the following year the catch increased slightly to reach 65 thousand tonnes (WB 2008). The total annual Caspian tul- ka catch in 2007-08 dropped again and was only 32.5 thousand tonnes. However, in Turkmenistan these statistics were reversed, with the annual catch increasing from six thousand tonnes in 1998 to 14 thousand tonnes in 2003. It is clear that the decline in the tulka fishery has been dramatic over the last ten years. This trend began in the 1980s and has persisted ever since, similar in character to the noted de- clines in the sturgeon fishery. The overall cause of the decline in the tulka fishery is at present unclear, although overfishing is undoubtedly one of the major factors (CEP 2007a). Overfish- ing had a clear impact on the anchovy tulka stock in the South Caspian (which comprised up to 90 per cent of the total catch) before the appearance of the comb jelly Mnemiopsis leydyi (ML) in considerable numbers. It is, however, difficult to separate the effects of overfishing and its competition with Mnemiopsis leidyi on anchovy tulka. ML are the main zooplankton feeders in the southern Caspian. Their inter- action is complex and may be influenced by other external factors. There are reports of ML appearing as early as 1995 - it is possible that up to the year 2000, the large tulka population prevented any significant ML bloom, and that it was only after subsequent sharp declines in the tulka stock, due to overfishing, that ML became a dominant threat, inhibiting the re- stocking of tulkas (CEP 2007a).
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