A shark in the Seine, hunting down swimmers. Sounds implausible, but that’s the premise of the new Netflix film Under Paris finning over, sorry, winning over critics.
‘It’s one of the best shark movies of all time,’ reads one.
‘At last, a shark movie worthy of swimming in the wake of “Jaws“,’ is the headline of another.
‘Adds life to a genre that’s been bloodless for far too long.’
High praise for a film that we all know, really, isn’t possible.
Or is it?
After all, the Seine flows into the Channel, the Channel is linked to the Atlantic, there are great white sharks in the Atlantic, and no walls in the sea.
That is all true, but there are walls in the Seine. Kind of.
Ali Hood, director of conservation at the Shark Trust, picks up the trail.
‘The Seine is some 485 miles long and navigable by ocean-going ships for 75 miles of that length, at which point both ships and sea creatures alike meet the first of many locks that sit between the open ocean and Paris,’ she says.
‘Several major cities are founded on tidal waterways, where salt and freshwater mix, and we do get the odd report of confused marine wildlife – from small whales and dolphins, to the occasional coastal sharks swept in on the tide. But not from Paris.
‘The diversity of sharks and rays in the English Channel is rich, but none of them show a predilection for freshwater, or the capacity to work a lock gate!’
The locks – six groups of them – seem like quite the plot point to hurdle, but then again, great whites can leap up to three metres out of the water, so that’s one option.
They’re also highly intelligent creatures, so perhaps tailgating behind a boat isn’t out of the question.
The far bigger issue is the freshwater found flowing through Paris. Well, fresh in the salty sense, not cleanliness.
‘Many sharks and rays are seen in estuarine – river mouth – environments where salinity remains high,’ says Ali.
Yes, that includes the Thames and other UK estuaries.
‘Relatively shallow, and potentially protected areas, estuaries can offer nursery or feeding grounds,’ she says. ‘So, what stops sharks venturing further inland?
‘Man-made obstacles aside, few sharks have evolved to tolerate a wide range of salinities, being unable to adapt to the physiological demands of regulating the water content of their bodies at different salinities – in short, fresh water would dehydrate them.’
Now, in Hollywood, a dehydrated shark may be a more bloodthirsty shark – got to boost that liquid intake after all – but in real life, most saltwater sharks that do stray too far inland tend not to be in any condition to go on a killing spree.
The last time a large shark was caught in central London, way back in 1787, it wasn’t in terribly good shape – although is suspected of having eaten a sailor at some point, on account of a silver watch in its stomach.
But that doesn’t mean there aren’t sharks that thrive in freshwater full time.
‘Freshwater sharks and rays are a thing,’ says Ali. ‘There are three recognised species of Glyphis, or freshwater, shark – the Ganges shark, the New Guinea river shark and the speartooth shark, with other unidentified species reported from rivers in Borneo.’
And there is also one very special species of shark well-adapted to swapping between seas and rivers.
‘Warm, shallow, brackish waters do appeal to one shark,’ says Ali. ‘The bull shark.
‘More usually found in tropical or subtropical coastal waters where they cruise slowly near the seabed, they have been noted far inland – some 700 miles up the Mississippi, in canals and golf course ponds on the Gold Coast in Australia, and in Lake Nicaragua, 12 miles inland from the Pacific ocean.’
But like other species, bull sharks are more at risk from humans than the other way around.
‘The nearshore and estuarine environment leaves bull sharks vulnerable to human impacts from habitat loss to overfishing,’ says Ali.
One third of shark and ray species are endangered, including the critically endangered Borneo shark, smalltail shark and lost shark among others.
Alongside competition for food from fishing, sharks are often trapped in nets, known as bycatch, while in some regions they are deliberately caught for their fins, which are cut off before the shark is thrown back in the water, where they slowly die.
Luckily, conservation organisations around the world, including the Shark Trust, are working to protect the more than 500 species of these fintastic creatures.
None of which will be appearing in the Seine any time soon.
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