Gambusia fish to curb spread of dengue

READ MORE R Damodaran
COIMBATORE: In a proactive move to curb spread of dengue, the district public health services would be distributing Gambusia fish to all Primary Health Centers (PHC) in the district.
For the first time the fish, which has been used in India since 1928, will be distributed to all 47 PHC's in the district to prevent the outbreak of the disease caused by mosquitoes, said R Damodaran, deputy director, Public Health Service, Coimbatore.

He said, the plans to distribute the fish have been taken up in order to curtail the disease, especially dengue, as a long term measure. The fish will be used to biologically control the disease in rural areas. It is found to be very effective and is continuously distributed in the Coimbatore corporation limits, helping to curb the growth of mosquitoes. Consequently, the spread of dengue reported in the Coimbatore region is the least when compared to any other district in the state, he said.

Damodaran said the fish would be bought from Mettur where it is bred and distributed to all PHCs. The fish will also be bred at the PHCs in a tub provided by the district public health centre, from where it would be distributed to health sub centres. The fish would also be released in water bodies and distributed to people visiting the centre for check up.

Damodaran said they are self-perpetuating after initial establishment. They continue to reduce mosquito larvae for long time. The cost of introducing larvivorous fish is relatively lower than that of chemical. Larvivorous fish such as Gambusia prefer shallow water where mosquito larvae also breed.

Gambusia fish can adapt to wide variations in temperature as well as to chemical and organic content of the water but does not tolerate very high organic pollution. The optimum temperature for reproduction ranges from 240C to 340C but the fish can survive at freezing temperatures. The fish frequent areas especially suitable for the mosquito larvae. It lives and multiplies in ponds stocked with larger fish provided the pond is shallow and has protective vegetation for refuge.

A single full grown fish eats about 100 to 300 mosquito larvae per day. It can tolerate salinity. It can withstand transportation and does not require any specialized equipment or containers, he added


Mosquito fish  (Gambusia affinis & G. holbrooki)

Photo credit: Chris Appleby, Gambusia holbrooki (female),  The United States Geological Survey
Credit: This web page was first developed by Jeffery B. Webb
DESCRIPTION
Mosquito fish commonly refers to either the Western or Eastern species of Gambusia. The two species are so similar that they until recently were considered the same species. This guppy-like fish is usually between one and two inches in length, silver to gray in color and resembles the common minnow. It is very adaptable, tolerant of a wide range of water qualities and its expansion is only limited by severe climates.
The fish have a large appetite, and a single female (which normally is larger than a male) can devour several hundred mosquito larvae per day. Gambusia can reproduce rapidly and are unlike other fish in that they do not lay eggs; they bear live young. Each female can produce three to four broods in her lifetime, and each brood can vary from 40 to 100 young. Birth usually occurs during the warm spring and summer months. When the young are born, they are active and immediately swim for the nearest cover. Though they are only about 3/8-inch long, they will soon feed.


mfish.gif (9155 bytes)
Credit: & Source: The Shasta Mosquito and Vector Control District 
gambusia.jpg (14202 bytes)
Credit: & Source: Gambusia Control Homepage
The upper fish is the female, note the gonopodium (a modified anal fin) on the male.
- Scalebar represents 1 cm.
(Source from: 1. The United States Geological Survey; http://nas.er.usgs.gov/fishes/accounts/poecilii/ga_holbr.html; 2. Mosquito fish: The Shasta Mosquito and Vector Control District, http://www.snowcrest.net/mosquito/fish.htm; 3. Gambusia Control Homepage, http://www.gambusia.net/)
IMPACTS
Mosquito fish have negative ecological impacts anywhere they are introduced. This a particularly predaceous species, easily out competing native species of minnow for available forage or harassing those competitors until death. They have been especially devastating in the American Southwest interacting with a wide range of threatened or endangered fish species; most recognized is the Gila topminnow. The decline of up to twenty species has been linked to the introduction of Mosquito fish outside of its native range. Recent studies suggest California's declining amphibian populations can be linked to Mosquito fish introductions as well.
On the other hand, there is a positive aspect of mosquito fishes. Mosquito fish are important to the mosquito control program. They eat mosquito larvae as fast as they hatch from the eggs laid by mosquitoes on the surface of the water. In California they are furnished alive and without charge for stocking ornamental ponds, unused or "out-of-order" swimming pools and animal watering troughs. They require no feeding and care is limited to protecting them from garden sprays and from chlorine or other chemicals used to clean the pond. The Shasta Mosquito and Vector Control District also stocks thousands of these fish each year in artificial lakes, reservoirs, waste water disposal lagoons, natural creeks and drainage channels to eliminate the need for frequent spraying with mosquito pesticides.
Source from: 1. James D. Williams, U.S. Geological Survey Biological Resource Division Henry R. Rupp, Adverse Assessments of Gambusia affinis, http:// www.nanfa.org/; 2. Mosquito fish: The Shasta Mosquito and Vector Control District, http://www.snowcrest.net/mosquito/fish.htm; 3. Gambusia Control Homepage, http://www.gambusia.net/)