west nile/mosquito/fish article
 

(remember jan's comment about frog population? She was
right on the money.)
County Uses Mosquito-Eating Fish To Control West Nile Virus
El Paso County Says It Will Be Careful Where Fish Is Stocked May 5, 2003

COLORADO SPRINGS, Colo. -- El Paso County health officials will use an
aggressive fish known as gambusia or mosquitofish this summer to try to control
mosquito populations that can spread West Nile virus.
Dan Bowlds, El Paso County's director of environmental health, said he found
the fish effective for the 2 1/2 summers he worked in neighboring Pueblo
County. Gambusia (pictured, left) will be used carefully, only in ponds that do
not drain into creeks or other free-flowing waterways, Bowlds said.
"You make an assessment when you see a body of water. Is this water going to
remain here all summer long? Does it look like it will support gambusia? And,
if it does, you'd prefer to use those. Then you've saved yourself a lot of
labor; you don't have to come back and treat it again," he said.
A professor who has closely studied the fish warns that gambusia are escape
artists, able to follow floodwaters to infest other waterways. "Once they get
established in a habitat, it's almost impossible to get rid of them," said Lee
Kats, professor of ecology at Pepperdine University in Malibu, Calif. "Our
evidence here shows once they get established in local streams, it's only a
matter of time before the native amphibians begin to disappear."
The El Paso County Board of Health's decision to add the controversial weapon
to its mosquito-fighting arsenal comes as agencies across the state combat the
threat of West Nile virus with a spirited search-and-destroy mission.
They're seeking out mosquito larvae wriggling near the surface of water bodies
-- small and large, permanent and temporary -- before those mosquitoes fly off
as adults to breed, feed and float more eggs.
Mosquito control experts know the habits of their prey from watery cradle to
grave and use that knowledge to destroy them. Rafts that float on the water's
surface, skeeter houseboats, contain up to 250 eggs.
The eggs need water to survive; draining stagnant water snatches potential
breeding ground from pregnant female mosquitoes. Larvae, or wrigglers, hatching
from eggs suck oxygen through air tubes, like snorkelers.
Experts lace standing water with larvicides such as Bacillus thuringiensis
israelensis, a naturally occurring disease among insects. Mosquito larvae die
after eating the genetically engineered bacteria.


k30a