Today’s News Hearld Sept 3,2009
Dead carp could help other fish in Lake
May result in population boom for other species

By TONY WAGGONER
Wednesday, September 2, 2009 10:13 PM MST
The Koi Herpes Virus had a devastating effect on Havasu and Mohave lakes, but now the carp die-off could help other fish species in both lakes.

Arizona Game & Fish fisheries biologists estimate the virus killed more than 20,000 carp, as it made its way down the Colorado River in spring and summer this year.

“There is really no way to tell what percentage of the carp died, though,” said Russ Engle, Game & Fish Region 4 fisheries program manager. “It appeared to be significant, but on the other hand, we don’t know what the population was in Lake Havasu.”

Carp are bottom feeders, which means many of the other fish in Lake Havasu could see an increase in reproduction this year, said Zen Mocarski, spokesman for Game & Fish. Hatch rates and populations of other fish like bass, catfish, bluegills, sunfish and crappie should increase with less carp feeding on their eggs at the bottom of the lake.

Game & Fish fisheries specialist Mark Brown said another benefit to existing fish is the increase in nutrients in the water. He said the dead carp rotting in the water was like fertilizer to other fish.

But fisheries experts say don’t expect the carp to stay away for very long.

“I’m sure the carp will rebound,” Brown said. “There is a constant biomass of carp in the Lake. I don’t doubt they would come back.”

When that would happen is unknown. Brown said the season for the carp to spawn coincided with the onset of the virus this past spring.

“An event like this creates a void that is generally filled pretty quickly,” Engle said.

And there is a chance KHV could make its way back into the river next year. Both Engle and Brown say it is a possibility, but without knowing exactly what caused the virus in the first place — many have speculated it was the introduction of a diseased goldfish or koi, while others have said it could have been the water temperature — it is difficult to know if it would reoccur.

Brown said several years ago Clearlake, Calif., experienced an outbreak of KHV and have not reported anything since.

What fisheries experts do say is this was the first time they had ever seen KHV in the Colorado River, and Brown says the first time is usually the worst.