Mosquitofish cut mosquitoes near abandoned swimming pools

Mosquitofish have been a swimming success for Richmond County Mosquito Control.


Dozens of miniature mosquitofish multiplied into hundreds of larvae-eating machines during a six-week trial program aimed at treating abandoned swimming pools that often turn into swampy mosquito breeding grounds.

“Where the mosquitofish are multiplying, the mosquitoes are not hatching,” said Fred Koehle, the operations manager for mosquito control. “That’s the goal.”

Koehle and his team of mosquito technicians launched a new program July 12 to control mosquito populations. About 30 mosquitofish the size of minnows were dumped into five pools in Richmond County. The fish had been lifted from Phinizy Swamp at no cost.

On Tuesday, the experiment continued as scientists from the Southeastern Natural Sciences Academy tried to count the fish with Koehle. Using equipment with two electrical probes to shock the water, the team hoped the voltage would temporarily paralyze the fish, making them float on the water surface to be counted. The shock treatment, normally used in shallow creek waters, did not work in the pool’s deep water.

The multiplication of fishes, however, was evident by the large number of minnows swimming around the green water and the absence of mosquito larvae.

“They are pretty prolific. They are worse than rabbits,” Koehle said.

At the beginning of the trial, a trap was set near each abandoned swimming pool to count the number of mosquitoes in a 22-hour period before the fish were released. The trap was set again after five weeks to compare the mosquito population and the program’s effectiveness.

At the house that scientists visited Tuesday, 180 mosquitoes were counted before the fish treatment. That number was reduced to 14 mosquitoes, Koehle said. The total from the five pools declined from 422 to 52.

“As far as we’re concerned, we’ve had a success,” he said. “It’s not going to be a cure-all, and we (won’t) get rid of every mosquito.”

The trial experiment also included a control pool in which fish were not released. The number of mosquitoes during a 22-hour period increased from 54 to 120, Koehle said. As the rainy summer progressed, more mosquitoes hatched during a few dry periods.

Koehle said he wasn’t disappointed when the electroshock process failed Tuesday. He hoped to determine more accurately how the fish were multiplying, but the reduced mosquito counts were enough to call the experiment a success.

Koehle wants to treat six more pools with mosquitofish in the next month. Eventually, all pools without a responsible owner in Richmond County will be treated with mosquitofish instead of larvicide, which costs $150 annually per pool.

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