A program involving experts and officials from eight European countries is working to repopulate the iconic Danube with the endangered beluga sturgeon. A century ago, when the Danube was still blue, it teemed with beluga sturgeon fish, as did the Rhine with salmon. But industrialization and the construction of canals and dams have destroyed the habitat of both species.

These interventions, and other forms of altering water flows, prevent both sturgeon and salmon from swimming upriver to deposit their eggs, a millennia-old ritual that has been thrown off course and is leading to the extinction of these species.

The overfishing of the beluga sturgeon (Huso huso) for its valuable black caviar has also contributed to its decimation. Today there are very few of these fish in the Danube, and even fewer salmon in the Rhine.

But the situation is about to change, thanks to a project involving environmental groups and officials in eight of the 10 European countries through which the Danube flows. The aim is to repopulate the river with the different types of sturgeon.

The Danube River Network of Protected Areas, also known as Danubeparks, is using sturgeon found in the river to reproduce more.

Danubeparks environmentalists in December discovered in the protected area of Drau, in Hungary, a rare bastard sturgeon (Acipenser nudiventris), which was taken to a breeding station for holding in hopes of finding a mate.

“It would be unconscionable to watch with arms crossed as the last of this species disappears after inhabiting the rivers of Europe for 200,000 years,” biologist Ralf Reinartz, of the University of Münster and coauthor of a sturgeon protection study used by Danubeparks, told Tierramérica.

The plan to reintroduce the sturgeon into the Danube requires a reform of the river's canalization in order to give the fish more freedom to swim.

Project coordinator Georg Frank explained to Tierramérica that, in the past, the canalization and construction of dams included the creation of so-called fish ladders, which allowed them to bypass the man-made obstacles.

“But given the size of some sturgeon, which can reach six meters, those ladders were insufficient for allowing the fish to swim upriver,” he said.

Frank also explained that some of the dams on the Danube were built in canyons so narrow that the construction of lateral ladders was impossible. One such site is the Iron Gate on the Serbia-Romania border, separating the south of the Carpathian Mountains from the north of the Balkan Mountains.

The Iron Gate is particularly harmful to sturgeons because it prevents access to an area where the Danube flows freely and would be ideal habitat for the fish.

As an alternative to the fish ladders, the repopulation project is considering transporting the fish using elevators – tanks filled with water that automatically climb past the dam several times per day.

This approach is already being used on the River Po in Italy at the dam near the northwestern city of Piacenza.

Apart from the obstacles that canals and dams pose for the breeding and survival of the sturgeon, the biologists of Danubeparks are faced with their own ignorance about the behavior of the species, according to Frank.

“We don't know much about the behavior and needs of the sturgeon at crucial moments in their lives, for example, when they lay their eggs,” Frank said.

To catch up, biologists and environmentalists along the Danube watershed are constantly exchanging information and experiences, he added.

The launch of the sturgeon repopulation project in the Danube coincides with the alarm sounded by the International Union for the Conservation of Nature (IUCN) on Mar. 18 about the possible extinction of the species.

The study published by the IUCN states that 85 percent of sturgeons, one of the most ancient families of fish existing today, is at risk of extinction. It is the group of animals most endangered on the Red List of Threatened Species drawn up by the organization.

The IUCN pointed out that the beluga sturgeon in the Caspian Sea, which flows into the Danube, has been classified for the first time as an endangered species.

“Beluga sturgeon populations have been decimated in part due to unrelenting exploitation for black caviar – the sturgeon’s unfertilized eggs – considered the finest in the world,” states the IUCN.

Phaedra Doukakis, a sturgeon biologist with the IUCN and the Institute for Ocean Conservation Science, said that given the risk of extinction, it is time to consider an end to fishing for this species in the Caspian and other areas where endangered fish species are found.