Biological mosquito control methods protect the public from mosquitoes and the transmission of mosquito-borne diseases. Mosquito biological control agents include a wide variety of pathogens, parasites and predators. A biological control agent used by the District is Gambusia affinis, the mosquitofish. Mosquitofish are small live-bearing minnows closely related to the common guppy. Used in mosquito control in California since 1922, these fish consume mosquito larvae and pupae and can survive in varying water conditions. Because mosquitofish are surface feeders, they are extremely efficient mosquito predators. Mosquitofish have been said to consume upwards of 80-100 mosquito larvae per day, and are capable of quickly populating a source if conditions are favorable. The fish are placed in a variety of permanent and semi-permanent fresh water habitats, including dirty swimming pools, water troughs, and ponds.