WWF’s release of more than 20 000 little sturgeons into the Danube a month ago is undoubtedly a promising conservation activity, aimed at boosting the number of the declining populations of Russian Sturgeons in the lower part of the river. In Bulgaria – where financial resources available to environmentalists and scientists are very limited, the sturgeon release was received with even greater excitement. The release itself is a spectacular activity to get involved in for every ichthyologist and it requires months of preparatory actions.
The work of WWF Bulgaria’s experts with the 3-month old sturgeons was not completed by simply moving them from the hatchery into the river’s waters. The most important part of their conservation actions actually started with the young sturgeons going back into their natural habitat. Next steps for Stoyan, Bobbie and their colleagues involve monitoring the movement of the Russian Sturgeons in an attempt to get to know more about their habitats, spawning sites and migratory routes. To track down a young Russian Sturgeon in its journey to the Black Sea is an even more difficult task this year than it normally is due to very high-water level, unusual for the season, and the numerous rainstorms. In general, data on the sturgeon migration habits is extremely limited, often old and unreliable. Among the reasons for that is lack of consistent financial resources for river monitoring, lack of expertise and technology as well as the lack of trained professionals.
The follow-up of the Russian Sturgeons release
A week after the release, the team of WWF Bulgaria returned to the exact spot in Belene where the little Russian Sturgeons had been transferred into the river to check if any of the fish could be found. While the WWF’s experts were in Belene, a fisherman in the outskirts of Vardim village, located 30 km downstream from Belene reported catching a young Russian Sturgeon. That meant sturgeons were indeed swimming towards the Danube Delta and more importantly, they were moving with the speed of about 30 km per day (24 hours). Stoyan Mihov, Chief Expert Wildlife and Freshwater, shared that “This is much faster than what we’ve expected! If they maintain this speed of swimming, they will reach the Black Sea in about 20 days after their release in Belene (rkm 574).”
When Stoyan and his colleagues went to Vetren to anticipate the arrival of the little sturgeons, soon it became clear that to find any of the little sturgeons in the poor weather conditions would be a matter of pure luck. It is not only the rainstorms that can affect the sturgeon movement – they may slow down or accelerate or go really deep in the river near the bottom of the riverbed to catch the fastest fairway. Again, the luck was with the fishermen that work closely with the WWF team and another Russian Sturgeon was found, weighting 29 gr., which is 20 gr more than when it was released. Both sturgeons looked strong, healthy and thriving in their new home. The fish showed visible signs of acquiring natural green-olive body coloration and full shape, instead of the “artificial” black and white and skinny appearance they would have if living in aquaculture facilities.
The WWF experts will continue their monitoring in the different parts of the Lower Danube, the Delta and the Black Sea coast throughout the most of the summer season, so stay tuned for more sturgeon updates.