Physical barriers in rivers have led to global, rapid declines in fish stocks
Although they outlived the dinosaurs, today up to 23 of all 27 sturgeon and paddlefish species are on the verge of global extinction according to the International Union for the Conservation of Nature (IUCN). The IUCN considers them the most threatened group of species on Earth. Four species are possibly already extinct.
The main reasons for the species’ demise are overfishing – which goes on despite the fishing bans in place in key sturgeon fisheries – and the human alteration of rivers. Physical barriers like dams block migration and disrupt the natural flow of rivers, which is critical for spawning. River channelization, straightening and navigation are also a problem.
In its new report, WWF calls for coordinated, global actions to help sturgeons and paddlefishes bounce back from the brink of extinction. “Now is the time, if ever, to take urgent actions to reverse this trend. A concerted, international conservation approach can help these archaic giants of the water remain a source of pride and livelihoods for centuries to come”, said WWF’s Global Conservation Director Deon Nel.
Until relatively recently, Bulgaria and Romania were among the worlds’ top 10 caviar exporting countries. Sturgeon populations plummeted after the construction of the Iron Gates in the 1980s – the biggest dam on the Danube. It confined sturgeons to 863 km of the Lower Danube and cut off important spawning sites in its middle reaches.
“Danube sturgeons used to travel from the Black Sea as far up as Vienna and further up to Germany, covering distances of about 2,000 kilometres! But such migrations have been impossible for a long time now”, said WWF species expert Jutta Jahrl. “Of the six Danube sturgeon species, one is now considered extinct, one is suspected to have met this fate, and three are critically endangered”, Jahrl said.
However, the situation of sturgeons is most dire in the Caspian Sea and the rivers draining into it. Dam construction on Europe’s longest river, the Volga, especially in its lower reaches in the 1950s, has turned the river into a chain of pools with slow-flowing waters full of blue-green algae and inflicted a mortal blow to all river species, but most of all to sturgeons.
The area has historically provided some 90% of sturgeon products globally and fetched average annual revenues of some €21 million for Iran and €17 million for the Soviet Union from 1976 to 1991. However, today all 11 Ponto-Caspian sturgeon species are on the brink of extinction.
“Communities in sturgeon range states like Azerbaijan, Bulgaria, Iran, Romania, Russia, Serbia, Ukraine and China, have thrived thanks to sturgeon fishing for centuries. The depletion of the stocks has made this impossible and it is crucial to open the hearts and minds of people and decision makers that protection of the species is a matter of utmost urgency”, said Irene Lucius, Conservation Director of WWF’s Danube-Carpathian Programme.
This problem of depleting stocks is not confined to sturgeons. The majority of native, commercial and recreational fish stocks are threatened around the world or are declining rapidly. Species like salmon, shad, giant catfishes, dourada and eels all migrate between the sea and the rivers to complete their life cycle and depend on free-flowing rivers.
Sturgeons, however, are special for their extraordinary cultural, commercial and ecological value. The species originated some 250 million years ago, when dinosaurs still roamed the Earth. They were depicted in Egyptian temples, appeared in poems by Ovid and Longfellow and were greeted by trumpets at feasts commemorating historic battles. They may also have inspired some Loch Ness stories.
The report Saving Sturgeons highlights the need to work in four areas to protect the species: addressing overfishing, identifying and protecting key habitats, doing conservation stocking and raising public awareness of the enormous cultural, commercial and ecological value of sturgeons.
You can find a summary of the report here.
You can read the full report here.
You can find sturgeon images here.