Are We Reintroducing The Wrong Sturgeon Species in Our Waters?



Atlantic sturgeon (Acipenser oxyrinchus) (Photo: Cephas, Wikimedia Commons)
Are We Reintroducing The Wrong Sturgeon Species in Our Waters?
post by
Reinout Verbeke

Using bone fragments found at archaeological sites, researchers from the Royal Belgian Institute of Natural Sciences have reconstructed the occurrence of sturgeon in the North Sea during the last 7.000 years. It appears that an unexpected sturgeon species was dominant in our region. Is this species the most suitable candidate for restocking and to save sturgeons from extinction?

Sturgeons are famous for their eggs, the caviar also known as ‘the black gold’. But the fish itself is also special. There are 20 different kinds of sturgeon, of which some can grow to a stunning 6 meters in length and 400 kilo in weight. Sturgeons are not only large but also long-lived: about 50 years on average, but century-old sturgeons are no exception. The scaleless fish with a dark back and white abdomen usually feed on small fish and shrimps. Most of the species live in the sea for years, before migrating upstream for spawning. Sturgeons have been on earth for about 200 million years, and are sometimes referred to as ‘living fossils’.

Another dominant species

Researchers always assumed that the European sturgeon Acipenser sturio was the sole sturgeon species living in the North Sea and Baltic Sea. This species, that once occurred in all European rivers and seas, is now only found in the Gironde-Garonne-Dordogne basin in France. Archaeological remains, discovered in the Netherlands, Belgium, Great Britain or France were blindly ascribed to the European sturgeon, until researcher Els Thieren from our Institute took a closer look at thousands of century-old sturgeon remains.

She found that about 6.500 years ago, not only Acipenser sturio occurred here, but also the Atlantic sturgeon A. oxyrinchus, a species that was thought to live only off the Atlantic coast of North America. The new study even demonstrates that the Atlantic sturgeon was the dominant species in the North Sea.

Which species should be reintroduced?

Most sturgeon species are threatened with extinction as a result of overfishing for caviar and habitat loss. The decline of the North Sea sturgeon population is also noticeable in the archaeological remains: starting from the Middle Ages, less and less sturgeon remains are found. Since the 1980’s, policymakers and environmental organizations are trying to reintroduce the sturgeon: A. oxyrinchus in rivers flowing towards the Baltic Sea, and A. sturio in North Sea rivers. In 2012, dozens of members of A. sturio, coming from Gironde, were released in the Nieuwe Maas, near Rotterdam and in the Waal near Nijmegen, both in the Netherlands. A similar operation was performed in the Haringvliet in 2015.

But are we releasing the right species? “Reintroducing A. sturio in our waters is not wrong, technically”, says archaeozoologist Wim Van Neer (RBINS), who supervised the study. “The species occurred here for thousands of years, but it was always outnumbered by A. oxyrinchus. Or maybe A. sturio is in fact a good choice, as the climate is changing and this species thrives in warmer waters. Policymakers may consider releasing both species and looking which species survives best. In any case, this study shows that we can learn a lot from the past to protect our environment today”.

The study was published in Journal of Fish Biology.

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