Caspian Sea 2011

2010

Caspian Nematodes have not been studied very much. It is probable that there are many endemic species, but they have not been identified on the species level. There are 62 species of Rotatoria in the Caspian Sea: two species are known to be endemic. Both species are found in the North Caspian Sea. There is no data relating to its introduction. Polychaete worms are not diverse in the Caspi- an Sea. Only seven species have been identified, of them introduced. All native species are seden- tary polychaete worms. The only vagile species is Nereis diversicolor, introduced intentionally in 1939 to improve the benthic community for fish feed- ing. One species, Parhypania brevispinis, is endemic to the Caspian Sea. All polychaete worms are an important part of the food chain and are a pre- ferred food source for many fish species. Oligochaete worms are more diverse. There are 20 species from 10 genera. Six species are endemic to the Caspian Sea. Maximum diver- sity is found in the North Caspian Sea with 19 species. All species are small, only measuring between 15 and 80 mm. In some locations, they are very numerous. All species serve as fish food, particularly for carp and gobies. Suctorial annelids (leeches) are represented by only three species, all of them distributed throughout the Caspian Sea, and only one spe- cies endemic to the Caspian Basin. Crustaceans in the Caspian Sea are numerous and diverse. Many species are endemic and are a significant part of the food chain. There are many forms of Crustaceans in the Caspian Sea, and some of them are of great importance. Cladocerans are numerous in the Caspian Sea. The composition of species differs in the North and South Caspian Sea. In the North Cas- pian Sea, 39 freshwater species of cladorean are identified. A total of 25 species are identified in the Central and South Caspian Sea, while only

10 species inhabit both the North and South Caspian Sea. Cradocerans are mostly dominant in the North Caspian Sea, with relatively small numbers existing in the South Caspian Sea. All Cladocerans are an important food source for fingerlings and planktonivorous fish. The tulka species represents up to 6% of food intake. Six- teen species (30 %) are endemic to the Caspian Sea and two species, Pleopis polyphemoides and Pe- nilia avirostris, are exotic invaders. Copepods are less diverse with 31 species, but they are very abundant, especially in the Central and South Caspian Sea. Sixteen species domi- nate and are distributed throughout the Caspian Sea. In the North Caspian Sea, these are joined by 14 additional freshwater species; one ad- ditional species is found in the South Caspian Sea. Seven species are endemic to the Caspian Basin and four are exotic invaders. Copepods are dominant species in the zooplankton of the Central and South Caspian Sea: these are a pre- ferred food for all planktivorous fish and consti- tute up to 90% of tulka food intake. Following the invasion of Mhemiopsos leidyi, the diversity of copepods was reduced in the South Caspian Sea, sometimes to only one species – Acartia tonsa. This is another invader in the Caspian Sea eco- system, only appearing in the Sea in the 1980s. Another two species of copepods, Oithona similis & Calanus euxinus, were found only between 2000 and 2005. These two species are new invaders. Two species of Barnacles were introduced into the Caspian Sea in the early 1950s. Their number is some- times considerable – it is rare that fish feed on them. Ostracods or seed shrimps are diverse with 48 species in the Caspian Sea. Of these 7 are endem- ic. All species are small – up to 1.3 mm in length. Opposum shrimps are small organisms – up to 40 mm – represented by 21 species in the Caspian Sea. Many species are distributed throughout the Sea. Numbers of opossum shrimps have fluctuated through the years, but the cause of this is unknown. 13 species, or 60% of this group, are endemic.

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