For biologist Zeb Hogan, the Mekong River that winds through Southeast Asia isn’t so different from the Guadalupe River east of San Antonio.
They are both vital to the surrounding ecosystem, critical to wildlife and humans, threatened by encroaching development and invasive species — and home to some of the largest freshwater fish on the planet.
For decades, Hogan has searched for big fish from South America to Asia to the Great Lakes. His explorations and research come to life with replicas from all over the world at a National Geographic program now at the Witte Museum.
On tour since 2016, the Monster Fish exhibit, which Hogan helped spin off from a National Geographic TV show in which he starred from 2009 to 2018, showcases the history and importance of species that can grow to more than six feet and weigh more than 200 pounds.
“There are about 30 species of fish out there that occur on every continent and it’s a diverse assemblage of fish,” Hogan said. “There are fish that you’ve heard of before like the giant carp or the giant catfish, but there’s also the air-breathing arapaima and freshwater stingray. About 70 percent of them are at risk of extinction.”
The exhibit at the Witte, which ends Jan. 22, spotlights a regional monster called the alligator gar, one of the largest fish in North America. It can be found in nearly every river system draining into the Gulf of Mexico, including the middle and lower Brazos and the Nueces, Frio, San Antonio and Guadalupe.
The Trinity River – which stretches from North Texas to Houston – is the world’s best fishing destination for the largest alligator gar. Distinguished by their long snouts and two rows of sharp, large teeth, they can exceed 300 pounds and eight feet in length.
Like the others, the alligator gar is an “indicator species” of the health of a river’s ecosystem. If they begin to decline, biologists can conclude that something is wrong — perhaps pollution or invasive species.
These fish are the world’s very real Loch Ness monsters, Hogan said.
“They are amazing and extraordinary creatures in their own right,” he said. “There’s so much going on in this world that most don’t even realize and we should protect that.”
In 1997, when Hogan first witnessed a Mekong giant catfish in the wild, his life changed.
At the time, it was the largest freshwater fish on record, and he was on a Fulbright exchange program in Thailand, researching the impact that proposed dams could have on the fishing community.
Hogan wanted to know what else was out there, if there was anything larger and how they were surviving.
From years of exploration, Hogan discovered that many of the fish were endangered from overfishing, habitat fragmentation and pollution.
In 2020, the International Union for Conservation of Nature declared the Chinese paddlefish extinct — a freshwater creature that could grow to around 23 feet.
Lake sturgeon, which can reach 300 pounds and eight feet in length, are at 1 percent of their population of a century ago.
“The danger now is that many of these fish will go extinct before people even know they exist. And to me, that’s really sad,” Hogan said. “They’re very rare, they’re hard to find and to study, but they are important.”
Big freshwater fish are some of the oldest around. Some, like the lake sturgeon and the alligator gar, can live more than 100 years in a healthy environment. And since they never stop growing, the oldest is also the largest.
But they might only live 10 or 15 years in degraded habitat, which is eliminating populations. Many of these species take years to reproduce, Hogan said. A sturgeon might not produce offspring…
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