Richmond County uses mosquitofish to treat abandoned pools



Tiny, mosquito-eating fish could be a big solution for abandoned swimming pools that have turned into breeding grounds for the pesky insects.

Richmond County Mos­quito Con­trol launched a new program Friday that uses mosquitofish to control mosquito populations at abandoned pools.

The fish, each about the size of a minnow, were lifted from Phinizy Swamp on Friday and put in four pools in the county.

“What we’re trying to do is save some money,” said Fred Koehle, the operations manager for mosquito control.

Mosquitofish are a less expensive and more effective method for treating swampy, neglected pools, Koehle said. It costs $150 annually to treat one pool with larvicide.

Mosquito control has treated 201 swimming pools. Of those, 150 were brought back into operation or filled in with dirt. The department has recently received 10 more complaints.

Koehle said the money saved by using mosquitofish he gets for free from the swamp can be spent for other mosquito issues.

Mosquitofish can be used only at abandoned homes where an owner cannot be located or lives out of state, Koehle said. He hopes to treat 12 pools during a six-week trial period.

Before dumping mosquitofish into the pool, Koehle and his technicians set a trap near the pool for 24 hours to count the number of mosquitoes that could lay eggs in the water.

Four pools each received 25 fish Friday. In two weeks, the fish will have multiplied ten times and will continue to reproduce, Koehle said.

“That mosquitofish does nothing but eat its main diet of mosquito larvae,” he said.

The fish are left in the pools until the houses are bought and the pools are cleaned by a new owner, Koehle said.

Once fish are in the pool, mosquito control needs to take very little action. In two weeks, Koehle will return to set another mosquito trap to test the difference made in the population.

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Gambusia affinis, or the western mosquitofish, is a small fish about 2½ inches long. They were introduced to the United States in the early 20th century and are increasingly used by public health departments to control mosquitoes.

Mosquitofish can eat 42 percent to 167 percent of their body weight per day. They feed on mosquito larvae, zooplankton or invertebrate prey at the water surface.

Some research shows mosquitofish can threaten other fish species when introduced into non-native environments.


Source: U.S. Geological Survey