Why you should care about freshwater “megafishes” | Zeb Hogan | TEDxUniversityofNevada


Translator: Tanya Cushman
Reviewer: Peter van de Ven On May 1, 2005, the fishermen of Hat Khrai village,
in Northern Thailand, were out on the river before dawn. It was the one time of year
to catch the Mekong giant catfish, a fish that Thais
call “pla buek,” or “buffalo fish.” Among Thai fishermen,
no fish inspires more folk tales, and the villagers of Hat Khrai have been telling stories
about pla buek for centuries. These fishermen
had watched their fathers, they had grown up watching their fathers pull dozens of Mekong giant catfish
out of the river every year. And they themselves had caught some, but it had been three years
since anyone, anywhere in Thailand, had caught a wild Mekong giant catfish. And it was clear that their numbers
were declining dramatically. Some people questioned whether or not there were any
pla buek left to catch. Together, the men ventured out
onto the muddy waters of the Mekong, unfurling their long nets
across the river. They’d been out on the water
for less than 15 minutes when the great fish announced itself
with four whacks of its tail. The fishermen knew immediately
what had tangled in their net. It was a pla buek. No other fish grew as big, and this one was enormous. It took the fishermen over an hour
to pull the fish to shore. And by then, the fish had lost
its brute force, its brute strength, that it exhibited out on the river. When one of the men thread a thick rope
through the fish’s mouth and gills, the toothless giant,
bruised and exhausted, put up little resistance. It took eight men
to lift the fish out of the water, to measure and weigh it. The fish measured 9 feet in length and it weighed 646 pounds. The fishermen didn’t know it at the time, but they had just broken the record for the largest
freshwater fish in the world. Or had they? At the time, I was working
in the Mekong Basin. I was doing research
that I’d started as part of my PhD. And media around the world
reported on this 646-pound catch, but no one was reporting
of anyone ever catching a larger fish. So the catch made me curious. I asked myself, “What is the world’s
largest freshwater fish?” We know that the African elephant
is the world’s largest terrestrial animal, that the blue whale
is the largest creature in the sea, that the whale shark
is the largest marine fish. But as I started digging, I realized that no one had ever looked
at giant freshwater fish on a global scale. And it was because of this curiosity
and my inability to find answers that I started to search
for the world’s largest freshwater fish. Together with the
National Geographic Society and the University of Nevada, Reno, it’s become a ten-year-plus
scientific adventure to six continents to find, study and protect
the world’s largest freshwater fish. And it’s been an adventure
that stretched across the globe, from some of the most
remote places on earth to our own backyards. And it’s also become
a race against the clock to try to find and protect
these giant fish before they disappear forever. What I found has been amazing, more incredible than I ever imagined. Beneath the surface
of the world’s rivers and lakes swim dozens of species
of mysterious aquatic giants. These are the real-life Loch Ness Monsters
of the freshwater world. There are about 30 species
of what I call megafish, freshwater fish that grow
to over 6-feet length or weigh more than 200 pounds, and it’s a diverse assemblage
of unknown, poorly understood creatures, like the giant Siamese carp. This is a fish, a 600-pound relative of the goldfish, that has scales that are the size
of the palm of my hand. Or the giant freshwater stingray, a stingray in fresh water
that can grow to 15 feet in length and has a venomous barb
on the base of its tail that’s as long as my forearm. There are two other species
of freshwater ray that grow almost as big. And one species in Northern Australia was only described in 2008. So these are enormous creatures that play important roles
in aquatic environments, yet their numbers are dwindling, threatened by overfishing
and habitat loss, pollution, climate change. Over 70% of these giant fish
are now at risk of extinction. So why are these fish, like this giant goonch catfish in India, why are these fish disappearing? And honestly, why should we care? Well, the big fish – often these big fish
face the biggest threats. They’re the first to be affected
by overfishing, by dams, by pollution a lot of times. And so they’re indicators, these big fish
are indicators of river health. And it’s not just big fish;
it’s small fish too. It’s all fish. The troubled story of these large fish underscores an environmental crisis
that’s facing our lakes and rivers today, where the rate of biodiversity loss,
freshwater biodiversity loss, is greater than the biodiversity loss
that we see in the oceans or on land. And it’s not just fish. It’s people too. You take the Mekong River as one example. The Mekong river is
the most productive river on earth. Over 2 million tons of fish are harvested
from the Mekong River every year. And as the big fish disappear
from the Mekong, it’s an indication that the overall harvest
is at risk as well. And that it turn threatens
the livelihoods and food security of millions of people
living along the Mekong river. These fish are culturally important. Giant Siamese carp, giant seven-striped barb, giant catfish are carved into the walls
of the ancient Angkor Wat temples in Cambodia. These are fish that are so significant that they play central roles
in religion and ceremony, that these extraordinary animals, they have the ability to change
the way that we view the world. I remember the first time
I saw one of these fish – and I hope some of you
are feeling the same way right now – the first time I saw one of these fish,
something inside me shifted, and my world became a bigger place. It became a better place. So what can we do
to save these amazing animals? First, I think we have to acknowledge
that they have an image problem. (Laughter) So first, I think we have to acknowledge
that they have an image problem. We tend to dismiss these fish as ugly. Let’s be honest: we tend to dismiss these fish as ugly or think of them as food or fear them as dangerous. But they’re much more than that. They are found in many
of the world’s great rivers. In the Mississippi, in the Amazon,
the Yangtze, the Nile, the Colorado. Like us, they need clean water to survive. They clearly illustrate threats
to aquatic systems, and they can be used to show the link
between river health and human health. We need to change the way
that we think about freshwater fish. As sharks have shown,
over the last 40 years, it is possible to change
lack of awareness and even fear to appreciation and respect. You think about – for those of you
that were around – think about how we thought about sharks
when the movie “Jaws” came out. And now, 40 years later, thanks to the work of thousands
of people around the world, people’s perceptions
of sharks has changed. And three of the largest shark species,
including the great white, are now globally protected. And an important part of this
is education and outreach. This is a photo of Cambodian children reading a book about the ecology
and conservation of Mekong giant catfish. Ten years ago, when I
was just starting this work, I would talk to people
or show people photos of these fish, and people hadn’t heard of them. Today, when I speak to students,
even young children, a lot of them can name these fish. And we need to come together. These fish, they don’t have many friends. They need more friends, and so we need to come together,
form partnerships, and especially,
engagement with fishermen. Those can be important conservation tools. An example of this
is what’s happened in Alaska, where fishermen, local businesses
and environmental groups have come together
to protect Bristol Bay, which is home to one of the largest
populations of salmon on earth. Or what’s happening in Mongolia, where scientists,
religious leaders and fishermen have come together to take the lead in protecting
the world’s largest trout species. And then, finally, we need action, direct action to help protect
aquatic habitats, help either maintain or restore
free-flowing rivers, and help save these iconic
yet critically endangered megafish. If you google “dam removal,” you can see an example
of one of the kinds of actions that are being adopted
more and more frequently recently to help protect these rivers and fish. I was back in the Mekong late last year, and I witnessed first hand
people coming together to try to create a world
where megafish and humans can coexist. While Cambodians were celebrating
Independence Day, a group of fishermen outside of Phnom Penh
made a very special catch. They caught the first
Mekong giant catfish of 2015. And that’s evidence that this extremely rare fish
still occurs in Cambodia and it’s still making
its annual spawning migration in the free-flowing stretches
of the Mekong. We tagged and released this fish, alive,
downstream of the fishermen’s nets as part of a partnership between the fishermen, the Cambodian department of fisheries and scientists. To release the fish,
I dove into the water with it to try to guide the big fish down
into deeper water. And about 15 feet below the surface, my ears popped, it was silent, it was dark, and I’d reached the point
where my world ended and the world of that fish began. In the end, I’ve learned that the search
for the world’s largest freshwater fish is about far more
than finding the big one. It’s the story of the health
of our rivers and lakes. It’s the story of people who depend
on fish and fresh water to survive. And it’s the story
of how we perceive our world and how the existence
of these amazing fish makes our lives richer
and earth a better home, not just for us,
but for all life, big and small. Thank you very much. (Applause)

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