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Mosquito
Fish Fact Sheet


The Mosquito Fish is a name used for several species of Gambusia, including Gambusia affinis and Gambusia holbrooki.  The name of the genus "Gambusia" comes from a Portuguese word, "gambusino" which means "useless".  Until the 1900's they were called "Top Minnows".  The name was changed to "Mosquito Fish".  They are now found in every continent except Antarctica.

The Mosquito Fish was introduced to many areas because they were believed to be good at controlling mosquito larvae (wrigglers).  In fact most fish eat mosquito larvae readily and it is often difficult to find any in water containing any sort of fish.

When I was in Mindanao in the Philippines I was surprised that there were so few Mosquitoes.  I tried looking for Wrigglers.  Instead I found at first that every little body of water, or even of mud had fish in.  Then I started to wonder; there were some Mosquitoes, where were they breeding?   I looked some more and found wrigglers in the top of each fence post.  The fence posts were made of thick bamboo and each one had a small area on the top with water in and the Mosquitoes were breeding in them.

Recent research has show that Mosquito Fish normally only eat about five percent of their diet as mosquito larvae while many fish eat more like twenty percent.

If Mosquito Fish have too high a percentage of their food as wrigglers they have trouble reproducing.

Rather than reducing the number of wrigglers, in many areas the Mosquito Fish have greatly reduced the number of native fish which are more effective than the Mosquito Fish in controlling Mosquitoes.  The large scale introduction of Mosquito Fish into other areas has failed to control Mosquitoes, but has done enormous damage to the ecosystems of these areas.

The attitude of people now to the Mosquito Fish in Australia is quite different from that in the Untied States.  In some areas, of the United States Mosquito Fish are still distributed free of charge.  In the areas that they were native to, this can sometimes make sense, but to do this in California where they were introduced in about 1920, and where they are threatening native animals like the California Newt is strange.

However, some of the authorities in the United States are starting to take notice of the danger of introducing this fish to their waterways, and the Mosquito Fish is restricted in some areas of the United States.

The Mosquito Fish is one of the many species introduced mainly by government action.  Other examples are in the article Ecological Disasters.

Why were Mosquito Fish used For Mosquito Control?

One reason was their name.  It was assumed that they must be good at controlling Mosquitoes.  If you watch Mosquito Fish you will certainly see them eating some wrigglers.  Another reason was convenience.  The Mosquito Fish can take an amazing range of conditions.  They can withstand temperatures from 33̊ F (1̊ C) to 100̊ F (38 ̊ C), salinities possibly up to twice that of sea water, are very easy to breed, and do not require any local research into native species.

Although it was easy to use Mosquito Fish, it does mean it was they were the best choice.  In Australia and in several other places of the world it is being recognized the using fish native to the area is better than using Mosquito Fish.  In the United States in areas that the Mosquito Fish in not native to, a fish native to the particular area would be more appropriate.  For example, Robyn of Robyn's Mosquito Fish Page uses Fat Head Minnows.

Sources

The department of Fisheries of the Government of Western Australia, Fishnote of The Government of the Northern Territory, NSW Department of Fisheries. The department of Fisheries of the Government of Western Australia, Department of Employment, Economic Development and Innovation, Queensland Primary Industries and Fisheries, Marion County Oregon, Robyn's Mosquito Fish Page, Gambusia Control Homepage, North American Native Fishes Association (NANFA),


 






 
Female Gambusia affinis
 
 
 
Female Gambusia affinis
 
 
 
Female Gambusia gaigei
 
 
 
 
 
 
Male Gambusia affinis
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