The Decline of the Sturgeons
The decline of Danube sturgeons is clearly documented by the rapidly decreasing catches.
Over the years, there has been no thorough monitoring of sturgeon populations in the Danube and their decline is hard to quantify. In general, assessing stock sizes of migrating fish in large water bodies is not easy. Danube sturgeons show a complex population structure with different life stages across the Danube River basin and the Black Sea.
However, the decline of Danube sturgeons is clearly documented by the rapidly decreasing catches. Already at the beginning of the 16th century, catches of Beluga Sturgeon dropped in the Middle Danube, and in the 18th century fishing of migratory sturgeons in the Upper Danube was abandoned due to their scarcity. The Lower Danube continued to be the ultimate stronghold of sturgeons until the fast decline in the last decades.
In Bulgaria, total annual catches fell from 63.5 t in the 1940s to 25.3 t in 1995-2002. In Romania they fell from 1,144 t in 1940 to less than 8 t in 1995. Identical decline in numbers of sturgeon fish was observed in Ukraine. In the last 150 years the Azov Sea sturgeon population suffered dramatic stock reduction. In all cases, the cause was overfishing. From 1927 to 2001 Ukrainian enterprises produced 49,000 tons of sturgeons. Thus, from 1990 to 2011 the number of sturgeons in the Azov Sea was decreased 120 times. The same scenario unfolded in the Black Sea basin. By 1980s, the sturgeon population had been growing because more than 50 million young fishes had been released into the Black Sea by Dnipro sturgeon restocking plant. However, in the late 1980s their quantity dropped to a minimum under the influence of unaccounted fishing and poaching.
As outlined above, the reasons for the dramatic decline of sturgeons are complex, but lack of awareness and information is a root cause of the most important one, overfishing.