Coachella Valley Mosquito and
  Vector Control District

MOSQUITOFISH
The widespread use of mosquitofish in control programs resulted in its worldwide distribution.  Initially introduced into California in 1922, the fish have become one of the most efficient natural methods for controlling mosquito populations.

BIOLOGY
The mosquitofish is a member of the family Poeciliidae.  The fish give birth to live young.  They are extremely prolific, breed throughout the summer and may have up to 3 to 5 broods annually.  Fertilized eggs hatch in 21-28 days. 

The young are approximately ¼ inch in length and may mature to a maximum size of about three inches. Each brood may consist of approximately 40 to 100 young.  The temperature range for optimal growth is 77-86°F (25 to 30°C).  Females continue to grow after sexual maturation but the males stop once they become sexually mature.  In the cold months the low temperatures cause the fish to become lethargic and feeding rates decrease.  Mosquitofish have a short life cycle, lasting 2 to 3 years. The small size allows them to dwell shallow waters and penetrate dense vegetation growth where larvae and pupae seek shelter. 

FEEDING
The Mosquitofish has a voracious appetite and feeds on plankton and aquatic insects.  The young fish are ready to feed immediately on mosquito larvae.  The flattened head and protrusible mouth enable the fish to readily prey on surface feeding mosquito larvae and pupae.  The fish are visual predators and feed during daylight hours.  Temperature and photoperiod influence metabolism, feeding rates, growth, sexual maturation and fecundity. 

 
ENVIRONMENTAL FACTORS
Mosquitofish can tolerate broad temperature changes, organic pollution, salinity, poor food supply and overcrowding.  Their hardiness, adaptability, ease of handling during transportation, and relative lack of susceptibility to disease contribute to their effectiveness.   

POTENTIAL STOCKING HABITATS
The potential stocking site habitats of mosquitofish are of an environmental sensitive nature in Riverside County because of the threat to an endangered species, the desert pupfish, Cypronidon macularius (Baird and Girard).  Therefore, state law requires a permit from the Department of Fish and Game for the transportation and stocking of mosquitofish.  The presence of other predators such as piscivorous fish and birds may also reduce or eliminate stocked mosquitofish.  Stocking the fish and maintaining optimal populations is a delicate process which requires continuous monitoring.  Some examples of mosquitofish potential habitats include:
Reservoirs - Ornamental ponds - Retention/detention basins - Unused swimming pools - Drains - Watering troughs -Ditches - Ravines - Flood channels -Marshes  - Wetlands - Waste-water facilities - Duck club ponds.
 

WATER TEMPERATURE AND QUALITY
Mosquitofish tolerate extreme temperatures from 33-108°F, yet prefer 88°F.  Important water quality factors to be monitored are temperature, dissolved oxygen, salinity, pH, ammonia, and turbidity.  These factors must be within optimal range for favorable mosquitofish growth and reproduction.                                                                                 
        
INDOOR AQUARIUMS AND SMALL ORNAMENTAL PONDS
Mosquitofish should not be combined with other species in aquariums or ponds because of the fact that they will often attack other fish by nipping at the fins and tails.  In aquariums, the young must be provided protection  from injury by providing hiding places such as dense growth of plants or a partition separating the fry from adult mosquitofish.

PUBLIC PICK-UP OR DELIVERY OF MOSQUITOFISH
If you have an ornamental pond, unused swimming pool, or an animal–drinking trough and you want to eliminate backyard mosquito breeding sources, mosquito fish will be provided to you at no charge.