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There is a widespread perception that the Caspian is in a state of ecological decline, and that one aspect of this is a decline in biodiversity.  This is of particular concern, due to the status of the Caspian as a unique water body inhabited by a large number of endemic species.  There is also a widespread belief that the Caspian is very sensitive to the impacts of industrial activities and in particular to those associated with oil and gas production and transportation.

The Caspian Sea, world largest lake, is bordered by Republic of Azerbaijan, Islamic Republic of Iran, Kazakhstan, Russian Federation and Turkmenistan. Out of 122 fish species and subspecies living in the Caspian Sea, 40 species are believed to be commercial and presently 25 species are the main exploited fish (Ivanov, 2000). At present sturgeons, tulka and Caspian Sea seals are considered as shared commercial stocks between Caspian Sea range states.

The data of long-term ecological studies (1999–2014) are used for assessing the impact of a new Caspian invader Mnemiopsis leidyi A. Agassiz, 1865 on marine and anadromous fish species. The introduction of the ctenophore and its massive development in the Caspian Sea have mainly affected planktophagous fish, especially the most abundant species anchovy sprat (Clupeonella engrauliformis Borodin, 1904) and sturgeons (Family Acipenseridae). Mnemiopsis leidyi is one of the main negative factors preventing the restoration of the populations of Caspian fishes, especially anchovy tyulka. The critical state of the resources of the spawning parts of sturgeon populations (Family Acipenseridae) has been reinforced as a result of the massive development of M. leidyi.

The seal is the only marine mammal in the Caspian Sea, feeding on tulkas and other small fish, and preyed upon by land animals. It is an endemic species for the Caspian Sea and is vulnerable on that point of view. During its life history the Caspian seal migrates from the frozen North Caspian waters in the winter to the South Caspian in the summer timer and back to the North to give birth to the pups on the ice. During these migration time the seals can be found everywhere in the sea.

Active conservation efforts will be required to assure the Caspian seal does not eliminate from the Earth. As a major mammal, anchoring one end of the food web, it also plays an important role in the biodiversity of the Caspian Sea and is a remarkable indicator of the Caspian ecosystems health.

The tourist brochure describes interesting species of flora and fauna of the Ural River Delta and the adjacent coastal zone of the Caspian Sea.

Toxicity tests are commonly used as a tool to determine the standards of water quality for chemicals and to discover appropriate organisms as bioindicators in toxicological studies, and also could be used as an essential tool for evaluation of the pollutant effects in aquatic ecosystems. The aim of the present study was to evaluate the sensitivity of two Caspian fish species, Caspian trout as an endangered species and Caspian Kutum using the static acute toxicity in response to nonylphenol, which is widely discharged into the Caspian Sea environment.

In addition, Caspian trout was approximately 6 times more sensitive than Caspian Kutum. Nonylphenol was reflected to be "highly toxic" to Caspian trout and "moderately toxic" to Caspian Kutum. The results could be considered in preparing plans for conservation and restocking management of Caspian Kutum and the endangered Caspian trout. 

This brochure has been produced on behalf of the consortium developing the hydrocarbon deposits beneath the North East Caspian defined under the North Caspian Sea Production Sharing Agreement of 1997.

The concession area lies in a region of rich biodiversity recognized as being of international importance for its wildlife, including several species that are classified as endangered. The widely varying conditions in the North East Caspian include extreme seasonal temperature variations, long-term sea level change, short-term sea surges and retreats, high levels of turbidity and sediment movement, ice cover in winter and scouring of the seabed by moving ice.

This dynamic environment presents challenges for those who live and work in the area. It also means that the fauna and flora on land and at sea, are adapted to a significant level of environmental stress from continually changing physical conditions. 

The main focus of review: To determine the Status of invasive species with special attention to the most aggressive invader Mnemiopsis leidyi in the Caspian Sea.

Objectives:

1. To assess vectors, pathways of invasive species introduction, their composition and their role in the Caspian ecosystem.

2. To analyze seasonal and interannual dynamics of the Mnemiopsis leidyi population in the all areas of the Caspian Sea; its impacts on the Caspian ecosystem including food recourses (zooplankton) and fish stocks along with other emerging environmental threats such as increased nutrient load from the coast, structural and quantitative changes in phyto-and-zooplankton communities, the appearance of harmful algal bloom (HAB) in the Southern Caspian.

3. To prepare recommendations for follow-up actions on invasive species management: - for the protection and control of the Caspian Sea from any sources of accidental invasive species introductions - for possibility of biological control of invader Mnemiopsis leidyi.

The primary source of this Review has been national reports from every of the five Caspian littoral countries, which included results of national observations of ecosystem state and biodiversity of the Caspian Sea. But due to fragmental data of the national observations on invasive species