General introduction

Sturgeons are a unique and fascinating group of fishes. They exist since more than 200 million years and lived when dinosaurs still roamed the earth. With their outer appearance and clad in bony plates they give the impression of ancient times, when it was necessary to carry armour to survive. Until today, they have survived almost unchanged.

Their occurrence is restricted to the northern hemisphere where they inhabit rivers and seas in Europe, Asia and North-America.

The Danube River and the Black Sea once were hotspots of sturgeon biodiversity as six native species were documented in the past. Today, one species is lost and the remaining five are threatened with extinction (IUCN 2010).

Although worldwide there are more than 20 sturgeon species with different needs regarding their specific biology and ecology, they all have some important common traits.

Sturgeons are among the largest freshwater fishes we have on our planet.

All sturgeons migrate over long distances for feeding and spawning. Some migrate between fresh- and saltwater, whereas others remain in freshwater for their whole life. They reproduce in freshwater and have a long life as they need several years, some even decades, before they become mature and are able to spawn for the first time. While annual spawning success is highly unpredictable and depends on available habitat, suitable flow and temperature, particular spawning sites are usually frequented periodically and migrations are predictable. Natural hybridisation can occur between all species.

All living sturgeons are endangered or threatened by extinction.

Sturgeons are also the source of caviar, the most expensive and exclusive food as status symbol. Therefore, they are targeted by both legal and illegal fisheries. Despite the fact that sturgeon females carry a lot of eggs, may spawn repeatedly in consecutive time intervals and thus have the potential to produce a lot of offspring, they need a long time to mature and populations suffer severely from the loss of adult spawning fish. Therefore, it takes a long time for sturgeon stocks to compensate for losses due to fisheries, they are easily overfished and the sustainable management of populations is a very difficult and complicated matter.

Their long spawning migrations and complex life-cycle, stretched out over vast areas in the sea and the river, also makes their movements predictable leaving them susceptible to specific fishing methods and making them vulnerable for the loss of spawning sites due to the blocking of their migration routes and modifications of the natural course of the river and its floodplain.

Main references

Reinartz, R. (2002): Sturgeons in the Danube River. Biology, status, conservation. Literature study. International Association for Danube Research (IAD), Bezirk Oberpfalz, Landesfischereiverband Bayern, e.V., 150 pp.

Bloesch, J., Jones, T., Reinartz, R. & Striebel, B. (2006): Action Plan for the conservation of sturgeons (Acipenseridae) in the Danube River Basin. Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention), Nature and Environment 144, 122 pp.