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Mosquito
Fish Hatchery
Special thanks to the
MDA |
Introduction
In an effort to control
mosquitoes with less reliance on the use of pesticides, the County of York,
Mosquito Control Division utilizes several approaches. In an integrated
approach to pest control, one aspect is the use of biological control
agents. An example of a biological control agent for mosquito control is the
mosquitofish, Gambusia holbrooki. When used correctly it is an
efficient, cost-effective, and environmentally sound method for the
control. The
Mosquito Control Division has constructed two 30,000 gallon
tanks shown here. 
Each holds several
thousand mosquito fish. Our intention is to breed these fish and stock them
into areas that breed mosquitoes. The species is Gambusia holbrooki. We are
one of the nine government fisheries that produce fish for stocking in
Virginia, and the only fishery in Virginia producing Mosquito Fish.
Mosquito Biology
There are nearly sixty
different species of mosquitoes in York County, and they may be found in
almost as many varieties of habitat. All have one point in common. They all
require, as part of their life cycle, standing water in which to develop. It
is in water where, as larvae and pupae, they spend a major part of their
life cycle. During these aquatic stages of their development mosquitoes are
most susceptible to control. It is at this point that mosquitofish, once
introduced, will opportunistically consume mosquitoes.
Mosquitofish Biology
 Gambusia
holbrooki, a member of the live-bearer family Poecilliidae, is a
species native to Virginia and widely distributed in the Chesapeake Bay
system.
The mosquitofish thrives in a
wide variety of water types, being very tolerant of high water temperatures
as well as very low dissolved oxygen levels. Mosquitofish give birth to an
average of 40-100 live fry, each of which is approximately 3/8" in length.
On average, 3 to 4 broods are produced each year, depending on the size of
the female and the length of the breeding season. Females can attain a
maximum length of two inches; males one inch. Both sexes seldom survive for
more than two years.
Throughout its development
G. holbrooki has a voracious appetite, feeding on a wide variety of
plankton as well as larger aquatic insects. It is a random feeder, with the
availability of food being more important than type.
Being opportunistic feeders,
other invertebrates and fish fry are readily consumed by G. holbrooki.
The mosquitofish has a number of natural enemies including wading birds and
various fish such as bass, pickerel and sunfish.
When to Stock
Early spring fish stocking
will be most efficient for season-long control. However, mid-season stocking
may be appropriate for areas which periodically dry back and re-flood as a
result of seasonal weather.
Which Mosquito Species?
Which Not?
In general terms. G.
holbrooki is attracted to moving, active prey. The feeding and respiratory
habits of the various mosquito species will determine Gambusia feeding
behavior. For this reason, mosquitofish may not be effective in controlling
some Anopheles or Coquillettidia mosquito species. In general, the use and
application of G. holbrooki should be by professional mosquito control
agencies only. No stocking should take place without first performing an
adequate mosquito survey and an investigation of the natural history of each
site. All stockings should be made with discrimination, and not randomly.
Habitat Types
Not all bodies of water are
suitable for introduction of mosquitofish (lakes, ponds and streams
generally are not considered as major sources of mosquito breeding). Some
examples of mosquito habitats where fish may be introduced include:
- Stormwater management
facilities.
- Ditches and swales.
- Dredge spoil impoundments.
- Artificial containers -
i.e., ornamental ponds, abandoned swimming pools and foundations.
- Excavated sites such as
farm ponds.
- Sewage lagoons and/or
waste-water facilities.
Gambusia should not be
stocked in natural wetlands or in areas where threatened or endangered
species of fish or amphibians are known to exist. Consult with the County of
York, Mosquito Division (890-3790) if there are any questions about the
presence of threatened or endangered species.
Gambusia Stocking
Rates
|
Habitat |
Number of fish |
|
Bird bath (large) |
10 per site |
|
Stormwater Facility |
1,000 per acre |
|
Ditches |
1 fish per yard of ditch
length |
|
Dredge Spoil Impoundments |
2,500 per acre
(immediate control) |
|
Sewage Lagoons |
1,000 per acre
(inoculation rate) |
|
Farm Ponds |
1,000 per acre |
For more
information, please contact the Division of Drainage and Mosquito Control at
757-890-3790. |
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