Caspian states backed an initiative on Tuesday to protect their shared sea from overfishing and oil pollution which is gradually destroying the world\'s main habitat for caviar sturgeon. Environmental groups say wildlife in the Caspian Sea is gradually dying out -- sturgeon stocks have fallen by 90 percent since the late 1970s. Iran, Russia, Azerbaijan, Turkmenistan and Kazakhstan signed the framework agreement, put forward by the United Nations Environment Program (UNEP), to tackle the problem. It is hoped the agreement, which the states have yet to ratify, will lead to a reduction in the amount of sewage and industrial waste pumped into the sea. \"By signing this important new treaty the Caspian states are demonstrating their firm commitment to saving the beautiful and resource-rich Caspian Sea,\" Iranian Vice-President Masoumeh Ebtekar said through state media. The sea is being increasingly tapped for its large oil reserves. But environmentalists want oil companies working in the Caspian to invest in equipment which is less likely to leak. (Reuters)