Colorado river dams decimate native fish

We may love our trout, smallmouth bass and green sunfish -- but these game fish are aliens in the Colorado and many other western rivers. Thanks to widespread damming, these "introduced species" are decimating the more fragile natives such as the Colorado's razorback sucker, humpback and roundtail chub, bonytail chub and pikeminnow.

The natives are more susceptible because their larvae are usually less developed when they hatch, and are less able to escape from predators, than those of the sturdier game fish, according to Alice Gibb, a Northern Arizona University scientist whose research was funded by the National Science Foundation. Before dams were built, native fish larvae could hide in sediment and turbulent water.  Now the large, still artificial lakes along the 1,450-mile-long river leave the native larvae "at a grave disadvantage," said Gibb, who presented her findings today at the Society for Experimental Biology's annual meeting in Marseille, France.

"We suggest to management agencies that, in addition to removing introduced predators of native fishes from key river reaches, efforts must be undertaken to re-create the high-flow, sediment-rich, warm waters that gave the Colorado its name," Gibbs reported. "Dam removal may be critical for rehabilitating fish populations across the U.S., and almost certainly in other, less-studied areas of the world."

So where's that Monkey Wrench Gang when it's needed?

--Margot Roosevelt

Photo: Confluence of the Little Colorado and Colorado rivers in the Grand Canyon. Credit: David Ward, Arizona Game and Fish

Comments

[sheila]

how many times do we have to show how incredibly harmful it is to ecosystems to "improve" them with ill-conceived profiteering? we cannot continue destroying pristine ecosystems for profit motivations.

why do people who value the perfect systems we start with on earth, and who recognize their value to all of us, end up being the marginalized outlaws (monkey wrench gang), and the people who dam, dynamite, mine, bulldoze and otherwise destroy nature, slaughter species and waste our opportunities are revered in some sort of sick "manifest destiny" mentality?

we have been brainwashed too long that killing off nature = "progress." all it = s is destruction, waste and loss, which is then socialized onto the environment, and mercenary capitalism, which then privatizes the ill-gotten gains. this is sick and wrong.

[Daniel]

Decimate means to reduce by a tenth. Does that mean that the native fish are being reduced by a tenth?

[Milo]

This isn't the only bad things that dams are doing to rivers. How many of us know that the Colorado River used to be red? I didn't before I started doing some research. Also, temperatures in the Colorado River have gone WAY down....in the forties all year-round. So not only are the fish dying because of predators, they are dying because they cannot survive in the river. I just think that humans should have never gotten in a war with Nature. We can't win.

[Lauren]

In response to the question about decimation, the population of some native fish species, such as the humpback chub, has been reduced by 95%. The statistics regarding other fish species vary, but across the board, the damage has been significant.