New Orleans Enlists Fish to Fight Mosquitoes in Swimming Pools

Craig Guillot
for National Geographic News
July 25, 2006
When floodwaters rushed into New Orleans after Hurricane Katrina last
August, they filled thousands of swimming pools with fish, pollution,
algae—even the corpses of dead animals.

Experts say the pools may now harbor another hazard—mosquitoes.

"We have thousands of pools. We know a bunch of them are breeding mosquitoes, and there's the potential for West Nile virus," said Steve Sackett, an entomologist with the New Orleans Mosquito and Termite Control Board (NOMTCB).

"We're concerned with pest problems, but we're really concerned with disease transmission."

(See National Geographic magazine's "New Orleans: Home No More.")

Using real estate databases, aerial photography, and old-fashioned legwork, Sackett and his team have identified more than 5,000 at-risk pools in the city.

Their research reveals that some abandoned pools harbor not only saltwater fish but mosquito species new to the city, including two of the main carriers of West Nile virus.

"One of the things that we've seen is a change in the mosquito species that were living in the pools. Where they came from I don't know, but we had quite a few of these larvae swimming in some pools," Sackett said.

So far this year, drought has helped prevent a mosquito outbreak in New Orleans. But pools remain a serious health concern, as the summer mosquito breeding season sets in.

Natural Solution

To battle the bugs, Sackett has turned to a natural predator—the western mosquito fish (Gambusia affinis).

The fish can eat up to a hundred mosquito larvae a day. And unlike commercial pesticides, the prolific breeders can replenish themselves.

Introducing 30 to 50 fish per pool helps jump-start a natural ecosystem, where the fish keep mosquito larvae in check.

To date the fish have been released into 940 pools, according to Greg Thompson, a NOMTCB research entomologist.

Sackett notes that many abandoned pools have already transformed into natural ponds or swamps and are more brackish than Lake Pontchartrain.

(See Louisiana map.)

"When that chlorine first burns off and the chemicals are gone, mosquitoes are going to invade it," Sackett said.

"Our concern is that for some [pools], we just want to make sure that predators get a handle on [the insect larvae]."

Jorge Rey, a researcher at the Florida Entomology Laboratory in Vero Beach, says that Gambusia have been tried and tested around the world as a natural way to control mosquitoes.

"I'm sure these pools [in New Orleans] aren't in very good shape. Gambusia can live from completely freshwater to saltwater. They're pretty well adapted to a wide range of physical conditions," Rey said.

Helping Hands

Finding an endless supply of mosquito fish, a place to keep them, and a staff to stock city pools is a daunting task for NOMTCB.

Since Katrina hit, Sackett is down to a three-person staff to battle mosquitoes.

(See "Hurricane Katrina: Complete Coverage.")

Via the U.S. Federal Emergency Management Agency, he enlisted the help of Operation Blessing International, a Virginia Beach, Virginia, nonprofit that helped Sri Lanka battle mosquitoes following the 2004 Indian Ocean tsunami.

The humanitarian organization supplied Sackett with mosquito fish, equipment, and volunteer staff to help release the fish into city pools.

On April 18, the first official day of the operation, seven teams of volunteers treated more than 200 pools in the city.

Since then, Sackett and Operation Blessing have been working to ensure a steady supply of Gambusia by raising them at the New Orleans Prison fish hatchery.

The nonprofit's CEO, Bill Horan, says his organization hopes to eventually supply the fish free of charge to anyone in the region who needs them.

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