MOSQUITO
FISH - SCI & TECH
News:
Mosquitofish, used to
fight mosquitoes, has become invasive in India
What's
in the news?
●
In the last few months, various government
and non-governmental organisations in Andhra Pradesh, mosquitofish into local
water bodies to address a mosquito menace that locals have complained about.
Key takeaways:
●
Wildlife biologists consider mosquitofish
to be among the hundred most detrimental invasive alien species in India,
researchers have found, based on a genetic study, that two species of the fish,
Gambusia
affinis and Gambusia
holbrooki, had taken over many ecosystems across the country, the
former especially in northeast India.
Mosquito
Fish:
●
Mosquitofish, a fresh water fish (G. affinis and G. holbrooki) are
introduced into ponds to control mosquito larvae by eating them.
●
The Western
Mosquitofish (Gambusia affinis) is a
North American freshwater fish.
●
The eastern
mosquitofish (Gambusia holbrooki) is
a species of freshwater fish, closely related to the western mosquitofish.
●
These species of mosquitofish originated
in the U.S. but now have become globally dispersed with notable adaptability
and a tendency to proliferate in freshwater ecosystems.
Food:
●
They typically eat zooplankton, beetles, mayflies, caddisflies, mites and other
invertebrates.
●
Mosquito
larvae make up only a small portion of their diet.
Characteristics:
●
Mosquitofish are small and of a dull grey colouring, with a large abdomen and have
rounded dorsal and caudal fins and an upturned mouth.
●
Mosquitofish are small in comparison to
many other freshwater fish, with females reaching a maximum length of 7 cm and
males a maximum length of 4 cm.
●
The female
can be distinguished from the male by her larger
size and a gravid spot at the posterior of her abdomen.
Breeding:
●
The fish has a high breeding capacity.
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A single female may produce between 900
and 1,200 offsprings during its lifespan.
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The young females have two gestations per
season, while the older females may have up to six generations per season.
●
A season lasts about 30 days and young
ones are released in broods of 25-30 at a time.
Use
in Mosquitofish in India:
●
Gambusia
have been a part of mosquito-control strategies for over a century in various
parts of the world, including India.
●
Mosquitofish
were introduced in India in 1928 as a biological control method against
mosquitoes.
●
The idea was that the newly introduced
species would prey on or compete with mosquito larvae, reducing the latter’s
population.
Concerns:
●
Despite being introduced with the
intention of controlling mosquito larvae, mosquitofish populations in India
have spread far beyond their original
habitats, causing severe ecological and environmental issues.
●
The adaptability of Gambusia has enabled
its survival on six out of seven continents, leading the International Union
for Conservation of Nature to declare it one
of the 100 worst invasive alien species globally.
●
They are notorious for their detrimental ecological impact, including
displacing and preying on native fauna, leading to the extinction of native
fish, amphibians and various freshwater communities.
○
They are known to eat the eggs of
competing fishes and frog tadpoles.
●
In India, mosquitofish affected the
ecosystem health of the lake after its introduction into the Nainital Lake in the 1990s to control
malaria.