Meet the Mekong Giant Catfish. It eats river scum, can weigh up to 770 pounds, has no teeth, and looks absolutely ridiculous. At the same time, these gentle giants are held in special regard in their native Cambodia — in addition to their status as an important cultural symbol, they’re still an important food source to the people who live alongside the Mekong River. But they’re disappearing quickly — having been listed by the IUCN as a critically endangered species in 2011.
Hydroelectric dams are a major contributor to the species’ decline. Before the Mekong River was dammed, it would experience a seasonal “flood pulse.” During a monsoon, the river would expand in terms of volume — the amount of water would increase nearly tenfold compared to the dry season. And the catfish evolved to take advantage of this flood pulse.
Dr. Zeb Hogan, an aquatic biologist who directs the Wonders of the Mekong project and who also hosted National Geographic’s “Monster Fish,” explains the ecological harm these “green” energy developments can cause:
“What dams do is that they block the flood pulse — they hold all that water. And what we end up seeing is a smaller flood pulse, which means there’s less of a trigger for fish to go upstream and reproduce, and there’s less water coming down for all the young fish to disperse. And that can have a really negative impact on fish populations.”
Hydroelectric power plants, like the Xayaburi Dam in northern Laos, significantly alter the hydrology of the river. While wildlife advocates like Dr. Hogan continue to petition Southeast Asian governments to limit the construction of dams, the future remains uncertain for this charismatic bottom-feeder.
