Yes. Often, the mosquitofish’s diet consists of large numbers of mosquito larvae and that is how they got their name. There are two types of mosquitofish, the western whose scientific name is Gambusia affinis, and the eastern whose scientific name is Heterandria Formosa. This article focuses on the western species.
In comparison to many freshwater fish, the mosquitofish is small. Females are larger than males, and the females have a gravid spot at the posterior of their abdomen. Their diet also consists of zooplankton, beetles, mayflies, caddisflies, mites and other invertebrates.
Both the male and female mosquitofish are small and have a dull grey coloring with a large abdomen. They have rounded dorsal and caudal fins with an upturned mouth. The females average length is 2.8 inches, which the male-only reaches 1.6 inches.
You will find them mostly in shallow water protected from larger fish. They can survive relatively inhospitable environments, resilient to low oxygen concentration and high salt concentrations (up to twice that of sea water) and temperatures up to 108 degrees Fahrenheit for short periods. Due to their ability to adapt to harsh conditions, and their introduction into many habitats for mosquito control, they are the most widespread freshwater fish in the world.
Being introduced in many areas with large mosquito populations in the hopes of decreasing the mosquito population, proved to be ill-advised. It was later found that most native fish were already controlling the mosquito population and introducing the mosquitofish turned out to be more harmful to the indigenous aquatic life than the mosquito population.
They have an aggressive behavior and have been known to kill or injure other small fish through competition. Currently, the mosquitofish is only slightly better at eating mosquitoes than destroying other aquatic species.
They have done some good. From the 1920s to the 1950s, they were a major factor in eradicating malaria in South America, southern Russia, and Ukraine. In 2008 in California and Clark County, Nevada, they were bred in aquariums to stock in stagnant pools of water to reduce the number of West Nile virus cases. When they were made available to residents, they could only be used on their own property and were not to introduce them into a natural habitat. The Chennai Corporation in India introduced 660 pounds to control their mosquito population in fresh bodies of water.