Freshwater giants are dying


Some of the most amazing creatures on Earth hide in rivers and lakes: giant catfish weighing more than 600 pounds, stripes the length of the Volkswagen Beetles, trout six feet long that can swallow an entire mouse.

There are about 200 species of the so-called freshwater megafauna, but compared to their terrestrial and marine counterparts, scientists study them little and little they know the public. And they are disappearing silently.

After an exhaustive survey of the entire Yangtze River basin, researchers declared this month that the Chinese rowing fish was officially extinct. The spatula fish, last seen alive in 2003, could grow up to 23 feet long and once inhabited many of China's rivers, but overfishing and dams decimated their populations.

Rowing can be an omen for many other giant fish. According to research published in August in Global Change Biology, freshwater megafauna has declined by 88 percent worldwide in recent years.

"This study is a first step," said Zeb Hogan, aquatic ecologist at the University of Nevada, Reno, and co-author of the research. "We want to go beyond the simple study of the state of conservation and look for ways to try to improve the situation of these animals."

For the relatively few scientists who focus on freshwater species, the news that the largest are disappearing is no surprise. Since Dr. Hogan began studying giant fish 20 years ago, he has witnessed the decline of many species, and now, the extinction of at least one, the Chinese rowing fish.

"The species that were rare when I started working on them are now critically endangered, and even some of the much more common ones have previously become rare," he said.

However, protections for freshwater bodies generally remain rare. While about 13 percent of the land in the United States is conserved, less than a quarter of 1 percent of its rivers are.

According to John Zablocki, river conservation consultant at Nature Conservancy, part of the problem is that people assume that rivers that cross land protected areas have the same protections by association. In fact, dams are often built inside national parks.

"The rivers are basically the red-haired stepson of the protected areas," he said. "If you look around the world, there are very few examples of rivers that are protected in some lasting way."

To change this, Mr. Zablocki, along with a growing group of scientists and advocates, is pushing for the creation of a global policy framework to protect rivers, something that has been in effect for a long time for marine and land systems. .

Meanwhile, grassroots interventions sometimes force a positive change in the absence of government commitment. Citizens of Bangladesh, New Zealand, Ecuador and several other countries recently obtained legal rights for rivers, which means that courts must treat these bodies of water as living entities.

Large dam projects in the Brazilian Amazon were suspended in 2018 after citizen protests and calls to move towards renewable energy. In 2012, protests in Chile contributed to the decision not to dam the Easter and Baker rivers, and instead install solar and wind farms for energy production.

In fact, as renewable energy prices fall, solar and wind energy are Become viable alternatives for hydroelectric power, especially in developing countries that have not yet divided their rivers with large dams, said Michele Thieme, a leading freshwater scientist at the World Wildlife Fund.