Zeb Hogan: I want you to come with me on a journey under water to see a world of colossal creatures, real life Loch Ness monsters.

Tonight, I would like to tell you the story a story of a ten-year scientific adventure to six continents on the search to find, study and protect the world's largest freshwater fish. Strangely enough this is what... my world looked like when I was growing up. I asked my mom to find some photos of me, fishing or doing something with fish and this is what she sent me. This was my childhood. Luckily not every place in Arizona is as dry as the area where I grew up. This is Havasu Creek, it's a tributary of the Colorado it flows into the Grand Canyon.

And I, as an undergraduate at the University of Arizona, my job as part of this larger team was to do surveys, fish surveys of the tributaries that flow into the Colorado. And that's when I really fell in love with water and learned to... ...sympathize more with fish. So, on the Colorado, I learned about endangered species issues. And most of the native fish of the Colorado that live in the Grand Canyon are endangered. One of the reasons these fish are endangered are because of all the dams that have been built on the Colorado. And those dams have completely changed the Colorado River.

And I also learned about large scale restoration projects. At that time, I don't if anyone has been watching the news, but they were doing what they call controlled floods. Releasing huge pulses of water down the Colorado to try to mimic the natural cycle, the natural seasonal cycle of the river. And I learned how difficult it is to restore a habitat that's been modified as heavily as a place like the Colorado. So, after I graduated from the University of Arizona, I took that knowledge and applied for a Fulbright Scholarship to Thailand. And spent a year in Thailand applying those same lessons to fish in the Mekong.

The Mekong is actually home to the largest inland fishery in the world. Over two million tons of fish come from the Mekong every year. In Thailand, I saw this 3,000-year old cave painting. I don't know if anyone can recognize what's on the top there. But giant catfish. 3,000 years ago people were painting giant catfish in Thailand. It shows you how important these fish were. I mean, they paint themselves and then the next thing they can think of to paint is these big catfish. They must've been important. As it turns out the Mekong has more species of giant fish than any river in the world. And it has species like the giant carp, a 600-pound goldfish.

The goonch catfish, you know, such a strange looking catfish, the little beady cat's eyes and nail-like teeth. And I heard stories of stingray, giant, powerful, stingray reported to grow up to a 1000-pounds. And then things really took a turn when this fish was caught. This is a 646-pound Mekong giant catfish. And it was caught in Northern Thailand in 2005. The fishermen here have been recording their catches since 1980 and it turns out that this was the largest freshwater, the largest giant catfish that they had ever caught. Some people thought that this might be the largest freshwater fish in the world. So, after this news went out, I was waiting to hear back from people, from different-- from the Amazon, from Australia, from different places with reports of larger fish. But I didn't, I didn't hear anything. We don't know what the world's largest freshwater fish is. One guy did get back to me. He said he caught a bigger fish than I did.

Zeb: And this... It's an important lesson because fishermen you gotta, you gotta watch out for fishermen. Because of stuff like this, because Photoshop's pretty easy these days, that actually makes the project more complicated because if you go online or you start looking at pictures, you start trying to get information there are some, some people that exaggerate out there. This is a photo and it's labeled Naga of the Mekong, Laos 1973. When I was doing my... first started my research you see this photo everywhere in Southeast Asia. And the Naga is a, is a mythical creature in Southeast Asia like the Loch Ness monster, that you see depicted on temples. But as it turns out, this photo was taken in San Diego in 1991. And somebody took the photo and, and repurposed it, and took it over to Asia and sold it to everyone over there. And so now people think that this is a fish, a freshwater fish, that lives in the Mekong. It's actually, I don't know if anyone recognizes it, it's an oarfish. It's a marine fish that washed up on the beach in San Diego and these are some military guys who found the fish washed up and they are holding it up for the camera.

A few years into the project we also started doing a television show called Monster Fish that we've been doing for six seasons now. So, now I'd like to share a few stories from... from the project and also some clips from the shows. I'd like to tell you about eels, longfin eels, the longest freshwater fish in New Zealand. They make these epic migrations. They are born in the ocean and then they find their way into streams and lakes in New Zealand... Live for sometimes over a 100 years. These eels are actually the slowest growing, or one of the slowest growing, of any fish. But they live so long that they still reach lengths of seven or eight feet. So, it's my job to swim down to see if I could find one of these big eight-foot eels. Here goes nothing. The eels, they're all surrounding me. Zeb: Suddenly, I realize they're not dangerous at all. They're some of the most curious predators I've ever seen.

Next I want to tell a story about the world's largest trout. And it's a story of a partnership. This is the world's largest trout. It gets six-feet long, 200-pounds. This fish is endangered. It's disappeared from China, most of China. It's disappeared from a lot of Russia but it still has a few healthy populations in Mongolia. And this photo was taken in Mongolia. And this is a photo of a five-foot taimen that swallowed a three-foot taimen and choked to death. And then in the three-foot Taimen, in its mouth, there was a one-foot taimen. So, I don't... maybe that's why they're endangered, right? They can't help themselves 

I don't know how many people, I know there are few people in the audience that have been to Mongolia, but you think of Mongolia and maybe you think camels, you think Gobi Desert but there are places in Mongolia that are lush, beautiful, green and these are the places where the trout, the taimen, lives. And this is the place where we had our project. Our project was a partnership between local people, recreational anglers and scientists. As scientists, we would go out and the fishermen would catch the fish, we would get our data and it worked really well. We had this project for five years. We were able to collect a lot of good information. And partially as a result of this project, the Mongolian government decided to make all fishing for taimen in Mongolia catch-and-release. So, now there's no more harvest of taimen. They're all released after they're caught.

And we also found... valuable information about these fishes. Age, their growth, their movement patterns. These taimen can live to be over 50 years old. And we found that their movement patterns, they would move to the same place, the exact same place in the river, year after year. And so sometimes you don't think about that, I certainly didn't think about it before this project, that you could be fishing and catch a big fish that has been sitting in that spot where you caught it for 50 years. Now that's pretty incredible.

Some of you may not know but there are stingrays in fresh water. There are probably 30 or so species of stingrays that live in fresh water. And three of those species are some of the world's largest freshwater fish. The first project that we had, it was on the species here the giant freshwater stingray that's found in Southeast Asia. And so we worked with the recreational anglers to catch, tag and release these fish to try to get information about their movement patterns. This is a video of us trying to catch one of these big fish so that we can get measurements and tag and release it.

Zeb: It's swimming around now. You can see it in the water. It's swimming around, it's trying to get out. Oh, there's the tail. There's the tail everyone, be careful! We got it. We have it! Wow! Oh! Here it is. We tied the barb to get a closer look. This could be the largest ray that I have ever seen. And it could be the biggest freshwater fish on Earth. Let's get a total length. It's 12-feet long, and now I really wanna get the width. It's seven feet, two inches wide. This is the biggest freshwater stingray I've seen. So, this ray is probably 400, maximum, 500 pounds. As big as it is, I don't think it's a world record. All right, there it goes. There you go. Yeah, nice. Yay! Awesome!

This is the second species of big freshwater ray. This is called a short-tailed river ray. And we were down in Argentina, trying to find this ray and we know next to nothing about these fish. One of the reasons why we don't know very much... They are camouflaged, they hide in the mud, they are so big, that fishermen down there when they hook into one, they don't even try to land it. They can't even bring it up with the fishing gear that they use. So, this is a species that's really in need of more study.

And then the third species of giant ray occurs in Northern Australia. And it could be the biggest of all the rays. There are stories of rays ten-feet in width. So, that... a ray of ten-feet width it would probably be 20-feet long. And that species, I have the video of it here, was only described in 2008. Zeb: This is the giant carp. So, the giant carp, it's now critically endangered. So there are very few of these carp left and the only place I know that it's still caught, is in Cambodia on the Tonlé Sap River, in the week basically before the full moon in November. And so you can imagine, if you are trying to study or better understand one of these fish and there's only one place, at one time of year in the world where you can find it, it's... it's a huge challenge.

And as you can probably guess, a lot of these fish are endangered. About 70 percent of them are at risk of extinction. This is a Chinese Paddlefish, found only in the Yangtze River. Very unusual fish, long slender fish with a sword-like snout that could get 20 feet long. And to my knowledge none of these fish have been seen in several years. So this could be the first one of these big fish that actually has disappeared. But my concern is that if we don't do something it might not be the last. 

One thing I just want to emphasize, these fish one thing they are not is... they are not dangerous. That fish, it might look mean but it's not mean inside. It's not mean inside. We've been swimming with pools and pools of 30 or 40 of these alligator gar and they don't, they don't give you the time of day.

So, what are some of the solutions? I'm not saying don't build any dams. I'm not saying we can't meet our needs as well. But let's do it in a smart way that's informed by good science. You think about the Mekong and what's sad about what's happening in the Mekong is that there are... there's very good information about where it might be a good place to build a dam or a bad place to build a dam. And unfortunately sometimes politics gets involved and we're not seeing some of those recommendations carried forward. So that's something I feel pretty strongly about. Next we have to remember that we are all connected to these fish. I mean, like people in the Mekong, 60-million people depend on fish to get most of their protein. And you might think “Ah, people in the Mekong, that's far away. Who cares about cute kids...” But if you, if you shop at Trader Joe's or Wal-Mart you are eating the same fish that those kids are eating. You thought White Ruffy sounds really nice, right? But it's actually, it is nice, but it's Mekong catfish. It's catfish that's raised in the Mekong Delta. And that's... huge amounts of it are exported into the US.

Third, I think these fish have an image problem. It's not the most beautiful fish. So, we need to get people excited about these fish maybe in a little bit different way, and I just... I put this picture up... Don't laugh, this is how I view the animal world. We just need to start thinking about these fish for the iconic, charismatic, long-lived fish that they are. They're some of the largest animals on Earth and they're... culturally important, they're indicators of the rivers, the health of the rivers, where they occur. So, when these fish disappear, a lot of times that's a signal to us that something's wrong. I also hear people, and this is something I'd like to bring up, I hear people say, Let's just leave the fish alone. Don't catch them, leave them alone. But the problem with that... ...mentality, I understand it, but the problem with that mentality is that there are so many threats to fresh water now, pollution, invasive species, dams, habitat degradation, climate change, that if we just leave the fish alone, the only difference that's going to make is that they're going to disappear... in silence. They're going to disappear and we won't even realize they're gone.

Because we need to be proactive. For me personally, this is, this is what my project is all about. Working with local partners to find, study and protect the world's largest freshwater fish. And right here, freshwater sawfish, one of the most critically endangered fish in the world. And really only found in healthy populations here at the Fitzroy River. I am hoping that the data we collect can help us put together a plan to protect them here and in other rivers. Okay, I am just going to push it forward gently... ...off the tarp. There it goes. We need to take action and that action can be as simple as practicing catch-and-release. Or being smart about what fish you eat. For someone who studies migratory fish, I've seen in the Colorado, in the Mekong, I've seen the problems that dams can cause... if they are not constructed properly, maybe not put in the right place.

And so one of the actions that has become an option over the last few years is dam removal. It's coming full cycle. From areas where we are building dams and causing problems for these fish to areas where we've realized that maybe the dam shouldn't be there any longer and we are removing them. So, this video was taken by a friend of mine, Andy Maser. And it's on the White Salmon River. It's a Condit dam. And you can see what it looks like to remove a dam from a river.

Scientists, they were expecting it to take perhaps three to four years for the salmon to come back into that area where the dam was. And they saw spawning salmon moving up past the dam site in the very first year. So, with that I would like to thank you and thank every one who has helped with the project over the last ten years. Good night.