Use Nature against West Nile

	I kid you not. This week’s Economist reports that with foreclosures in Southern California, houses have been abandoned, leaving countless swimming pools unmaintained and creating a newfound breeding ground for millions of mosquitoes. This has created an outbreak of West Nile Virus. Record numbers of dead birds have been found, and human cases are expected to follow. Until health officials can get this situation under control, you could use conventional methods like mosquito repelent…. Personally, though, I’m a big fan of the creative solution from county inspector Bill Bobbitt. This clever fellow has filled any standing water breeding grounds with mosquito fish (Gambusia Affinis), the all-natural way to eliminate mosquito larvae.
The mosquitofish (Gambusia affinis) is a species of freshwater fish, also commonly known simply by its generic name, gambusia, although such usage is ambiguous. It is sometimes called the western mosquitofish, to distinguish it from the eastern mosquitofish (G. holbrooki). In Hong Kong, it is also known as the live-bearing tooth-carp. It is a member of the family Poeciliidae of order Cyprinodontiformes. These fish are native to the watershed of the Gulf of Mexico, where it has long been known that they feed readily on the aquatic larval and pupal stages of mosquitoes. They are remarkably hardy, surviving in waters of very low oxygen saturations, high salinities (including twice that of seawater), and high temperatures; they can even survive in waters up to 42 °C for short periods. For these reasons, this species may now be the most widespread freshwater fish in the world, having been introduced as a biocontrol to tropical and temperate countries in both hemispheres, and then spreading further both naturally and through even further introductions. The majority of these introductions were foolish; in most countries where mosquitofish have been introduced it is has been proved that the endemic fish species were already providing maximal mosquito control, and that the introduction of Your Ad Here mosquitofish has been both unnecessary and highly damaging to endemic fish and other endemic aquatic life. In Australia G. holbrooki has caused great damage to native fish and frog species. For example it is considered responsible for the extinction of rainbowfish in sub-tropical streams around Brisbane. The mosquitofish is a small and stout, dull grey, robust fish with a rounded tail and a terminal and upward-pointing mouth adapted for feeding at the water's surface. In these features and their small size they resemble the tropical guppies, which belong to the same taxonomic family. Sexual dimorphism is pronounced; mature females reach a maximum overall length of 7 cm (2.5 inches), while males reach only 4 cm (1.5 inches). Sexual dimorphism is also seen in the physiological structures of the body. The anal fin on adult females resembles the dorsal fin while the anal fin of adult males is pointed. This pointed fin is referred to as a gonopodium and is used to deposit sperm inside the female.
	Females can reach sexual maturity in only six to eight weeks, and they may bear three to four broods of young in a single season. The first may number only a dozen, but later broods include 60 to 100 young. Females store sperm in their reproductive tract for up to two months and give birth to live offspring. Live-bearing gives their young a much higher survival rate than in most species of egg-laying fish, which typically suffer from egg predation. Under favourable conditions, mosquitofish live two to three years. Estimates of their breeding potential have therefore demonstrated an incredible ability for this species to multiply and dominate new habitats into which they have been introduced. Their success in a new environment is almost guaranteed by their rapid maturation, by breeding several times a year, and producing broods of around 50 advanced live young. Individual populations have been recorded expanding from 7,000 to 120,000 in five months.