The National Park Service is still urging people to stay out of the water along an 8-mile stretch of Lake Mead’s Overton Arm, but a health scare that cropped up there over the weekend may turn out to be bad news only for carp.
The Park Service issued the advisory Saturday, after a volunteer spotted “an unusual number” of dead carp along with a mysterious white foam in the water at the lake’s northern tip.
Lake Mead spokeswoman Christie Vanover said the foam and dead fish were found from the mouth of the Virgin River to as far south as Echo Bay Marina.
The Southern Nevada Water Authority is now testing samples taken from the area and expects to release the results later Monday.
Authority spokesman Bronson Mack said carp are the only dead fish found so far, which hints at some sort of virus rather than “a toxic substance” affecting all living things in the reservoir.
Lake Mead supplies about 90 percent of the drinking water used in the Las Vegas Valley, so officials are treating the situation with what Mack called “an abundance of caution.”
“We want to know what’s happening for obvious reasons,” he said. “We’re not noticing any water quality issues at our treatment facilities, but we’re monitoring.”
Vanover said the advisory to swimmers will remain in effect until the source of the fish die-off is known. Visitors are advised to avoid any activities that might put them in direct contact with the water in the Overton Arm, she said.
All of Lake Mead remains open to boating and fishing, “though I don’t know that I’d catch and eat any fish until we know more,” Vanover said.
In 2009, thousands of dead carp washed up in Lake Mohave, downstream from Hoover Dam, just before Memorial Day weekend. That die-off was eventually traced to Koi herpes, a fish virus that thrives in warm water, kills carp in large numbers but does not affect humans.
Contact reporter Henry Brean at firstname.lastname@example.org or 702-383-0350.