Total catches declined from about 40,000 t in 1991 to 8,500 t in 1997 and have partly recovered since, to an estimated 15,000 t in 2008. Because of the limited data available, it is impossible to assess whether fisheries management in the Turkmen sector of the Caspian is currently sustainable. Overfishing of kilka and other bony fish in the Caspian Sea has been a problem since at least the 1970s, its effect on stocks may be aggravated by pollution. Throughout the Caspian Sea, catches of the species declined by more than 58 per cent between 1993 and 2006.