The sturgeon is just as rare as the giant panda or the Siberian tiger, but there are ninety around it again

And they slip away from a tub into the spacious water of the river. Ninety young European sturgeons were deported on Saturday in the Waal near Woudrichem. During a thunderstorm and in the pouring rain they were sent away from a beach to the sea, for research and hoping that they will return in a few years to reproduce. The sturgeon is a majestic fish, say connoisseurs, who can be five meters long, three hundred kilograms heavy and sometimes one hundred years old in nature. At the event in Woudrichem, the sturgeons are only a year and a half old, about thirty centimeters long, and marked with a floy taga kind of label with which they can be identified.

There are 25 different types of stire in the world. “And 85 percent are seriously threatened,” says Niels Brevé. “They are just as rare as the giant panda or the Siberian tiger.” Brevé is a researcher at Sportvisserij Nederland and Wageningen University & Research. Last year he obtained his PhD on the possible reintroduction of the European sturgeon (Acipens Sturio), A grand program whose deportation is a taste. The species is almost extinct in Europe, it only swims in the mouth of the Gironde at Bordeaux, France. In the Netherlands, the last sturgeon was caught in 1952 in Tiel, one hundred and fifty kilograms heavy.

When the females are mature, they come back to reproduce in the water where they were born

The fish are grown in the Bordeaux area and a number of them were transferred to the Netherlands last week. It is not the first expansion. Five times earlier, since 2012, stricts were deported in Dutch rivers. The results of those tests are encouraging. The sturgeons are occasionally caught at sea and put back, and then turn out to grow to a meter or two. Brevé: “That is where it is bursting with food. And we have to have that. When the females are mature, they come back to reproduce in the water where they were born. We are waiting for that in France, Germany and the Netherlands.”

The fish know exactly where they come from, and feel free to swim a few hundred kilometers a day. If the females ultimately reproduce – and they do that from the age of fifteen to twenty – they produce huge amounts of eggs. “That can be 500,000 per female. Just think of Kaviar.”

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Water pollution

The fact that the sturgeon is extinct in the wild is a result of overfishing, water pollution and the construction of dams, locks and weirs. “But we keep hoping,” says Brevé, especially courageously drawing out of the improved water quality in the Rhine, and from the fact that fishermen now release the sturgeons again. For the sturgeon it would be a blessing if the locks of the Haringvlietdam were open regularly, attractive if the water is there because of the many food, the shallows. Brevé: “In the ideal world, seen from the fish, both the Haringvlietdam and the Afsluitdijk are open considerably.”

How attractive that brackish water is, is evident from what some previously set sturgeons did. They swam on the North Sea via the Nieuwe Waterweg, and then bend back to the outside of the Haringvlietdam. Very often the locks of this dam are not open, partly because in that case too much salty water flows into the land, which hinders the intake of fresh water. The crack opens at high river discharges but remains closed in dry summer months.

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“In practice, the sturgeons hardly opt for Haringvliet because they can’t get out well,” says Maarten Bruns, team leader at nature organization Ravon. That is one of the many organizations that cooperates in the research into reintroduction of the sturgeon, including the World Wildlife Fund, Sportvisserij Nederland, Ark Rewilding Nederland, Zoetgaarde Blijdorp, universities and governments of France, Germany and the Netherlands.

Seagull

New in the study is the start of a “breeding center” in Blijdorp in Rotterdam. Since last week, the zoo also has young stalks from France, and grows it up to turn it off once they have grown. Why? Brevé: “Young stricts are susceptible to predation. They are often eaten by thick fatty cins, bass and cormorants. I even experienced a sturgeon that fell out of the sky in Stellendam after he was picked up by a seagull.”

We already have an aquarium with seven million liters of seawater, so we are used to

Due to a stay in Blijdorp, the sturgeons must become larger and more resilient. “We already have an aquarium with seven million liters of seawater, so we are used to,” says Mark de Boer, head of Oceanium of Blijdorp. In addition, a ‘flow system’ will be added, with river water in a sea container, for example at the Nieuwe Maas. “That will be a big job.”

In that container, the sturgeons can get used to the Rhine, the water with which they have to become familiar to want to swim back to sea years later. “It would be nice if we could build something in which the animals let themselves be imprinted,” said De Boer. What Blijdorp ever wants to achieve is this: “That if you are on the Erasmus Bridge, a sturgeon can swim through it.”

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