Biggest American freshwater fish in danger

This video says about itself:

[White] Sturgeon at the mouth of the Harrison river, a tributary to the Fraser river in Canada.

Dammed if we do, dammed if we don’t: New World’s biggest freshwater fish at risk

By John Platt

Two of the world’s biggest freshwater fish are in big trouble, come reports from scientists in North and South America.

First up, the genetically distinct Kootenai River population of white sturgeon (Acipenser transmontanus), North America’s largest freshwater fish. This massive monster has been known to reach almost six meters in length and weigh half a metric ton, but its size hasn’t offered it any protection. In fact, it has made it more attractive, and the species has historically been heavily overfished.

The problem in the Kootenai River isn’t overfishing, although it is man-made: Montana’s Libby Dam, built in 1974. The dam prevents the river from the very flooding that used to tell the sturgeon it was time to spawn. Before the dam was built, an estimated 10,000 white sturgeon lived in the river. Now, just 500 remain, and they have not spawned in the wild in 35 years. Oops. …

Arapaima

Meanwhile, in South America, another of the world’s largest freshwater fishes—in fact, the largest species with scales—is also in danger of extinction, if it even still exists. A paper in the December issue of the Journal of Applied Ichthyology reports that the giant Amazonian arapaima (Arapaima gigas) are threatened by weak and unenforced fishing regulations in Brazil, despite the species’s protected status under the Convention on International Trade of Endangered Species of Wild Fauna and Flora (CITES).

Arapaima can reach more than four meters and weigh more than 180 kilograms. The fish actually comes to the surface to breathe, leaving it vulnerable to fishing with spears and nets.

Part of the problem with preserving the arapaima is that it has never really been studied, until now. Authors Leandro Castello and Donald Stewart examined several arapaima samples in museums and found that only one of them was actually the Arapaima gigas. “Our new analyses indicate that there are at least four species of arapaima,” Castello told BBC News. “So, until further field surveys of appropriate areas are completed, we will not know if Arapaima gigas is extinct or still swimming about.”

The Threadfin acara, Acarichthys heckelii, is widespread in the Amazon basin: here.