3 October 2020 | New Scientist | 45Graham Lawton is staff writer
at New Scientist“There seems to be a will to protect the
Yangtze’s fish stocks and ecosystems,” he says.
“So there could be positive effects from this.”
One immediate action was a moratorium on
fishing in 332 designated areas, which will be
extended to the whole river and all of its
tributaries next year. That is a start, says Jarić,
but fishing bans don’t always work and can
make matters worse. “If there is not good
control, people just switch to illegal fishing,
and then there’s even less control.”
And fishing bans don’t address the bigger
issue of dams. New ones usually have fish
gates to allow migratory species to swim
freely up and down stream, but they rarely
work as well as advertised, says Jarić. “Even if
they are constructed, they are usually not as
efficient as we want, some migration occurs
through them, but not as much as is needed.”
Dams remain an issue for river animals
worldwide. A recent assessment of the
world’s longest rivers found that only
37 per cent of those over 1000 kilometres are
completely free-flowing. These are restricted
to the Amazon and Congo basins and remote
regions of the Arctic. “It’s pretty unrealistic
to say don’t build any dams,” says Jähnig.
“But if we really want to build them – which
is really a questionable thing, they have so
many negative effects – can we move them
to a certain part where maybe biodiversity
won’t be that much affected?”
Despite these obstacles, efforts to save
the megafish are under way. In Europe, for“ The animals bearing the brunt
of this neglect are the 80 or so
species of really big fish”
example, sturgeon restoration projects
are gathering momentum. The last
remaining wild population of the
European sturgeon – which 150 years ago
was common in every major river system
connected to the North Atlantic, including
those in the UK – is clinging on in the
Gironde river in France. Ditto the Adriatic
sturgeon in the Po in Italy. Captive breeding
programmes are attempting to restore
those populations to healthier numbers,
while programmes are also under way to
reintroduce European and Baltic sturgeons
to rivers in Poland and Germany. Whether
these can succeed isn’t clear, says Jarić.
“We don’t know if they can establish
stable populations, the rivers are still
heavily fished, polluted and degraded.”
In the Americas, the picture is brighter.
“The Amazon river basin is reasonably
fine still,” says Jähnig. On the Juruá river,
which feeds into the Amazon in Brazil,
sustainable fishing projects have even
allowed the pirarucu, an air-breathing
megafish, to make a comeback.
In North America, strict conservation
measures have allowed other species to
turn the corner. The Alabama sturgeon
is probably lost and gone forever, but the
lake and Atlantic sturgeons are showing
signs of recovery. “None of them are really
doing well,” says Jarić. “They are still critically
endangered, but many populations have
a positive trend.”
In the Mississippi, meanwhile, another
critically endangered megafish seems to have
dodged extinction and has a shot at recovery.
The US river is even more degraded than the
Yangtze, but somehow its own weird fish, the
American paddlefish, is doing relatively well.
The loss of its Chinese cousin remains a
reprehensible and irreparable loss. But maybe
after 50,000 years of big animal extinctions
at the hands of one uniquely destructive
megafauna, we are finally learning to
look after the giants that remain. ❚In the Amazon, the pirarucu
(left) is making a dramatic
comeback, but the Yangtze
river dolphin (below) is now
almost certainly extinctMARK
CARWARDINE/NAT
UREP
L.COM