The World's Forgotten Fishes - 13

© WWF / Will White CSIRO Marine & Atmospheric Research

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SHARKS PATROL THESE (FRESH)WATERS!
" We have very little idea of the geographic distribution of these
sharks, much less their general biology. They show up like ghosts,
few and far between, in a handful of scattered localities.
Finding one is cause for celebration. "
Leonard Compagno, IUCN shark expert

Of all the freshwater fishes that we know next to nothing about, the five river
sharks of the Glyphis genus are among the most mysterious. IUCN estimates that
only 2,500 speartooth sharks remain in the mangrove-lined rivers of Australia
and New Guinea. Even less is known about the other species. Our knowledge
of the Irrawaddy river shark goes back to a single 19th century specimen from
Myanmar, and we don't have much more to go on when it comes to the Borneo
river shark. The New Guinea river shark and India's Ganges river shark make up
the vanishingly rare quintet; all those assessed by IUCN are categorised as
Endangered or Critically
Endangered.

New species of river shark, Glyphis garricki,
discovered in 2008 in Port Romilly,
Gulf District, Papua New Guinea

Did you know that freshwater
fishes include some of the smallest
vertebrates on earth, such as a minnow
that lives in peat swamps in Indonesia
and is just 8mm long and weighs in at
0.004g? Or that the mammoth fish of
the Mekong - the giant catfish, giant
freshwater stingray, giant barb, and the
wonderfully named dog-eating catfish
- can all grow over 3m and tip the
scales at more than 300kg?
And while many are simply silver,
others have made breathtaking use
of the world's colour palette. Like the
bright red and blue of the cardinal
tetra or the vivid red stripe along the
side of the denison barb or the red
spot of Australia's crimson spotted
rainbowfish.
Speaking of the crimson spotted
rainbowfish: science has shown that
they can actually remember things

for around a year - one third of their
lives 8 . While archerfish treat water
as a hunting tool, spitting it like a
projectile to knock unsuspecting prey
into the water. Africa's elephantfishes
use weak electrical pulses to
communicate with others about
sex, size, predators and prey. South
American leaffishes - as their name
suggests - mimic dead and decaying
leaves to catch their prey unawares.
And Siamese fighting fish build a
nest of bubbles for their eggs.
While we're on the subject of parental
care: the female spraying characin
in the Amazon lays her eggs on
overhanging leaves and the male
is then tasked with keeping them
moist until they hatch by constantly
squirting them with water. Equally
fascinating are the mouthbrooding
cichlids found in Africa and South

America, which protect their
eggs and fry in their mouths.
Meanwhile, some daffodil cichlids
forgo the opportunity to breed
and choose instead to help parent
the offspring of relatives9. Less
admirable behaviour is seen in
another Lake Tanganyika species -
the cuckoo catfish. Like its famous
avian namesake this fish tricks
another species into caring for its
offspring. It does this by creating
chaos at spawning time, and confusing
unsuspecting female cichlids into
scooping up the spawn of the cuckoo
catfish, which they subsequently
brood in their mouths.
And we haven't even delved into
the 11,000 species that migrate at
some point in their lives (see boxes
on gilded catfish, European eels
and sturgeon).
The World's Forgotten Fishes page 13
The World's Forgotten Fishes

Table of Contents for the Digital Edition of The World's Forgotten Fishes
