Carp die-off at Lake Mohave due to a virus

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June 10th, 2009

Poses no known threat to public health

A virus has been identified as the probable cause for a carp die-off in Lake Mohave.

Koi Herpes Virus (KHV) – which can impact carp as water temperatures warm in late spring – impacts gill function and can lead to suffocation and/or secondary infections. While there were bacterial issues, lab tests show KHV as the primary cause of the die-off.

“This is not a threat to public health, and it is not affecting other wildlife,” said Andy Clark, fisheries program manager for the Arizona Game and Fish Department’s Kingman office. “However, people should still avoid handling the dead fish along the shoreline and, until this die-off ends, we’d suggest anglers avoid taking carp and focus on the other species the lake has to offer.”

Clark added that this is not a water quality issue, which would have impacted all species of fish in the lake.

In the middle of May, carp began washing up on shorelines along Lake Mohave and within a week, the numbers began to multiply.

Arizona Game and Fish Department fisheries biologists visited Lake Mohave shoreline areas to examine the extent of the die-off, with the dead numbering in the thousands.

The gills of the carp had white spots along the sides and lacked blood.

“The lab test results are close to what we expected,” Clark said. “We recognized the need to get a sample, but it wasn’t that simple. We needed a live specimen, and carp we found close to the surface were dying shortly after capture.

“The problem was, we suspected this to be viral, and a virus dies when the host dies.”

After Clark managed to secure several live carp, they were shipped to Washington Animal Disease Diagnostic Lab (WADDL) for testing. The results came back late Friday afternoon.

While Lake Mohave remains the primary area of this die-off, there have been several recent reports at Lake Havasu. However, while that number remains low, it is possible KHV is the cause.

If a die-off begins at Lake Havasu, Clark said there’s little that can be done to stop it.

“There’s no method in place to change the water temperature in a short period of time that might prevent this,” he explained. “However, I want to remind everyone that we have no confirmation that an event of the same scale will occur on Lake Havasu. Only time will tell.”

As for a possible end to the die-off at Lake Mohave, Clark is uncertain, but believes we’ve already seen the worst.

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