Tests reveal cause of Lake Mohave carp die-off

As always, Memorial Day weekend brought a lot of visitors to Southern Nevada, many who sought rest and relaxation along the lower Colorado River. But this year the holiday brought something else, at least at Lake Mohave. Thousands of dead carp began washing up on the shoreline just before the early holiday arrivals.

Someone once told me that company is a lot like fish: They both start to smell after a couple of days. I can’t say the company was all that bad this year, but add a little sun and it didn’t take long before the dead carp began to stink. A biologist friend described the scene as carp Armageddon. The good news was that carp seemed to be the only fish affected.

Fisheries biologists with the Arizona Game & Fish Department collected samples of live carp and sent them for testing at the Washington Animal Disease Diagnostic Lab at Washington State University.

When I learned about the die-off, I decided to dig around to see if anything similar had happened elsewhere. I didn’t have to look long. A Google search using the phrase “carp die-off” returned multiple hits. It seems similar events occurred at lakes as far away as South Carolina and Canada and as close as Clear Lake in California in 2008.

Tests by the California Department of Fish & Game showed the cause of the Clear Lake die-off to be Koi Herpes Virus. Tests on the Lake Mohave samples came back this week and confirmed the same for the local die-off. The good news is this virus doesn’t affect humans.

According to researchers at the University of Florida, KHV can cause mortality rates as high as 100 percent among common carp and it manifests itself when water temperatures are between 72 and 81 degrees. Signs of infection include white spots on the gills.

“The lab test results are close to what we expected,” said Andy Clark, fisheries program manager for the Arizona Game and Fish Department. He expects the worst of the die-off is over but recommends fishermen avoid the carp and focus their efforts on other fish. Had this been a water quality issue, all fish species in Lake Mohave would have been impacted.

• FISH FOR FREE — Fishing without a license in Nevada will net you a trip to court and a fine as a general rule. But those outcomes will not occur Saturday on Free Fishing Day, when no license or stamps will be required. Bag limits and other regulations will be in force, however.

Free Fishing Day events are scheduled around Southern Nevada. At Floyd Lamb Park, the Southern Nevada Junior Bucketmouths will host a bass fishing derby for anglers ages 17 and under. The youth will compete in three age classes: 10 and under, 11 to 13, and 14 to 17. Registration opens at 8:15 a.m., and the derby will run from 8:30 to 11:30.

The Nevada Department of Wildlife and the National Park Service are hosting an event for anglers and would-be anglers of all ages at Boulder Harbor, formerly the home of Lake Mead Marina. This is a noncompetitive event, but the first 400 kids between the ages of 2 and 15 will receive a small tackle box and chances to win rods, reels and other prizes. Prize drawings for adults also will be conducted.

Registration opens at 7:30 a.m., and the event will run until 11.

If you’re up for a road trip, head to Eagle Valley Reservoir near Pioche, where Nevada’s Division of State Parks will host its annual Free Fishing Day Derby. Participants will have the chance to win prizes.

For more information, contact ranger Ben Johnson at (775) 962-5102 or 962-5103.

Freelance writer Doug Nielsen is a conservation educator for the Nevada Department of Wildlife. His “In the Outdoors” column, published Thursday in the Las Vegas Review-Journal, is not affiliated with or endorsed by the NDOW. Any opinions he states in his column are his own. He can be reached at doug@takinitoutside.com.