Click the link to read the article on the AZCentral.com website (Brandon Loomis). Here’s an excerpt:
August 25, 2024
A shot of cold water from Glen Canyon Dam appears to have stalled a smallmouth bass invasion of the Grand Canyon and protected rare Colorado River fish there, federal officials say. In early July, two years after first finding the predatory bass spawning below the dam and in threatened humpback chub territory, the U.S. Bureau of Reclamation began releasing cold water from deep in Lake Powell in an effort to chill the river past the temperature at which bass are known to reproduce. So far this summer, numerous netting, snorkeling and electrofishing trips on the river have turned up no newly hatched bass, biologists reported to an advisory committee meeting on Grand Canyon’s South Rim on Thursday.
“That’s huge,” said Kelly Burke, executive director at Wild Arizona and its Grand Canyon Wildlands Council, which had pushed for flow alterations from the dam to disrupt the bass invasion.
Cooler water was a must for preventing possible biological disaster this summer in particular, she said. “It couldn’t be better timed. We’re having an extraordinarily hot summer.”
The initial success also means the National Park Service will not dump a fish-killing chemical into spawning grounds a few miles downstream of the dam this year as it did last summer. Last year’s effort drew a rebuke from some tribal officials associated with Grand Canyon, who prefer nonlethal controls. Federal officials considered the bass invasion an emergency requiring quick action to prevent a population explosion that could devastate humpback chubs, 90% or more of which live in the Canyon. Cooling the river below 60 degrees Fahrenheit has at least stalled that explosion.