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Press Release

Vector Control Gives Away Free Mosquitofish

June 11, 2003

If you have a pond in your backyard and are worried that it might become a breeding ground for mosquitoes that might be carrying the West Nile virus, the county's vector control district is giving away free mosquitofish as an effective, ecologically sound way to control mosquitoes.

Mosquitofish (Gambusia affinis) have a huge appetite for mosquito larvae - an adult fish can eat as many as 500 larvae a day - and are therefore an excellent biological tool for mosquito control. The Contra Costa Mosquito and Vector Control District (CCMVCD) breeds up to one million fish every year, which are available for pick-up only (please bring a container such as a two-pound coffee can with lid) at the CCMVCD office at 155 Mason Circle in Concord. For ponds 15 feet by 15 feet or larger, phone CCMVCD prior to arrival to arrange for pre-bagging of fish. Directions to the office and a map are available online at

"Residents are a crucial line of defense against mosquitoes and therefore also against the West Nile virus, which is transmitted by mosquitoes to humans and horses from infected birds," says Deborah Bass, CCMVCD's Public Affairs Officer. She points out that the number one source of mosquitoes is residential and that homeowners and residents have an important role in controlling mosquitoes, which is also the best way to prevent the virus from spreading. She urges residents to eliminate any standing water found in tires, buckets, clogged rain gutters, etc.

Bass recommends that horse troughs also be stocked with mosquitofish, adding that horse populations in other states were hit hard by the virus, and that having mosquitofish in their water supply is not an equine health hazard. She also advises that horse owners have their horses vaccinated against the West Nile virus. An equine vaccine exists, although a human vaccine doesn't.

"We are unique among mosquito control districts in that ours is the only district in the nation to breed "albino" mosquitofish. Albino mosquitofish have an unusual and beautiful yellowish-white color, and are valued as a more ornamental alternative to standard mosquitofish. Right now, only a limited supply of albino mosquitofish is being offered to the public, in addition to the standard mosquitofish" says Bass.

For more information about mosquitofish, mosquito control or West Nile virus, call CCMVCD at 925-685-9301 or visit their website at

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Press Contact
  • Deborah Bass
  • 925-685-9301 x 112