As a continuing effort to control mosquitoes by way of the most
efficient, economical and environmentally sound methods, mosquito
larvae-eating fish have played an important role in New Jersey.
Both saltmarsh and freshwater marsh native fish species have been
encouraged to inhabit sites of mosquito production. The introduction
of the mosquitofish, Gambusia affinis, has been an integral
part of this effort for decades and decades.
The pitfalls associated with using this species have varied. State
and federal regulations regarding their use have been unclear.
Stocking permits for this activity have been restrictive, difficult
to understand and to obtain. The biology of the fish, its habitat,
larvivorous efficiency and its colonization have often times eluded
even experienced field biologists. Finally, the cost associated
with the commercial procurement of Gambusia has made its
full introduction into many programs, a luxury. The approximate
cost of the fish obtained from commercial hatcheries at this time
was approximately fifty cents each.
In 1990, as a result of a working relationship with the NJ Division
of Fish, Game and Wildlife, an opportunity arose which inspired
the concept of directly involving that Divisions Bureau of Freshwater
Fisheries in the colonization, stocking and surveillance of Gambusia
affinis.
The initial intent of the program was to offer a state source
of G. affinis at little or no cost to the counties, make
available stockable populations at times when "native"
sources were unavailable (i.e. in very early spring, or after
some sort of field mortality from drought or freeze) and to eventually
develop a winter-hardy strain for counties which were unable to
overwinter their own populations.
In order to determine the potential for use of such a developing
state program by the twenty county mosquito control agencies,
a survey of them was performed. Of the fourteen who responded
to the questionnaire, twelve indicated that they would want to
participate in ' such an opportunity; one county indicated that
they reared their own Gambusia and one indicated that personnel
restrictions would prevent them from participating. The range
of numbers of individual fish that counties were requesting was
from less than 1,000 to over 100,000. The survey also stimulated
many of the same questions that prevented many from dealing with
mosquitofish in the first place, such as stocking rates, habitat
type, environmental tolerance and health maintenance.
In the spring of 1990, the Office of Mosquito Control Coordination
met with representatives of the Bureau of Freshwater Fisheries.
The initial conversations were optimistic enough to realize that
Bureau personnel felt that a production cost of twenty five cents
per fish could be achieved. A "Memorandum-of-Understanding"
was drafted which included a "Scope of Work," "Records
and Reporting," a protocol for rearing and distributing the
fish and all associated costs.
At the April, 1991 meeting of the NJ State Mosquito Control Commission
the members unanimously passed a resolution which committed them
to the development of the State Biological Control (mosquitofish)
Program, and dedicated $2,000 in "seed money" to start
up the Program, and $10,000 a year thereafter.
The most valuable acquisition, however, was the involvement and
new-found working relationship with the Division's personnel.
This valuable resource soon proved to be indispensable. Prior
apprehension about the others understanding of fish and mosquito
management soon disappeared.
Later that spring, state biologists and staff from the Warren
County Mosquito Commission, went to work collecting field populations
of Gambusia from sites that had been previously stocked
with fish which were obtained from a commercial hatchery in Nebraska.
Soon, a healthy population was established at the Charles O. Hayford
State Fish Hatchery at Hackettstown. By summers end, at least
one county in southern New Jersey took receipt of the first state
stock of mosquitofish.
During the following winter, Freshwater Fisheries Bureau biologists
undertook a literature search on the subject of mosquitofish.
What was found were the references in this bibliography, articles
in the Journal of the American Mosquito Control Association and
some work in fish and wildlife journals. There was very little,
however, on the subject of use in New Jersey, little on mosquito
control efficiency, little on alternative (to Gambusia)
mosquito control fishes and little on the impacts to non-targets
in the mosquito habitat. One native New Jersey fish that did seem
to interest biologists for mosquito control was the freshwater
killifish, Fundulus diaphanous.
The staff and representatives of the State Mosquito Control Commission
encouraged the faculty of Rutgers and the State University of
New Jersey to submit project proposals to study particular subjects
which relate to the use of mosquitofish in the state. At the same
time, the NJ Mosquito Control Association's Research and Development
Committee (composed of biologists from each county) dedicated
themselves to coordinating their field data on mosquitofish in
order to make recommendations on the subject to the State Commission.
The staff at the Division continued to perform some limited field
surveys on the Gambusia population and advise using counties.
Meanwhile, they responded to some minor issues raised by contradictory
environmental commentators. While these comments were determined
to be unfounded and soon quieted, the Program continued to search
for agencies which may perform the research needed to balance
the use of almost 90 years of success with Gambusia, without
any environmental impacts.
The operations of the program soon became established. In order
to ease the burden of management for the Division and to align
the program with the procedures of the other programs of the state
mosquito commission, it was arranged to have the State Office
of Mosquito Control Coordination in Trenton administer and manage
the counties use of the program. All areas are surveyed by a state
and/or county biologist and are approved by the state before stocking
takes place. Stocking procedures, rates and surveillance strategies
are all reviewed.
The transportation and stocking may take many forms. Hatchery
equipment may be used, such as one of their own 5,000 gallon capacity
transport trucks. At the suggestion of hatchery staff, the mosquito
commission purchased three, 200 gallon and one 77 gallon capacity
transport tanks, with oxygenation systems. These tanks are removable
and transferable from county to county on their own pick-up trucks.
These afford the opportunity to more easily schedule and transport
fish at the convenience of associated staff. The oxygenation system
allows for a longer holding and stocking period. The hatchery
even has the capacity to mail approximately 500 fish, in containers
of super-oxygenated water, overnight.
The Program staff decided to commit itself to a constant state
of self-evaluation in order to improve. An assessment of the productivity
of the hatchery was performed. In 1991, 5,000 fish were stocked
and an overwintering stock was moved to an indoor facility in
order to be ready for spring. Much was learned about captive-fish
rearing during this time as breeding, diseases, mortality and
other aspects of Gambusia biology were experienced.
In the season of 1992, 40,000 mosquitofish were stocked in eight
participating counties. The effective cost per fish was twenty
five cents, thus reaching the prices-per-fish goal set by the
Bureau initially. In 1993, 57,500 fish were stocked and in 1994,
107,500 fish were stocked at costs of seventeen and nine cents
per fish respectively.
The using counties were again surveyed, this time to evaluate
how the program was doing. Responses were encouraging. All counties
supported the continuance of the program, now in its third full
year. Many county programs noted a reduction, or a complete elimination,
of pesticides used in areas where mosquitofish were stocked. Some
noted that hatchery-produced fish seemed healthier or more vital
than what they had been calling their "resident" mosquitofish
populations. Participating county mosquito control programs also
called their involvement with the state biological control program
a public relations "bonanza. " The production of even
more mosquitofish was encouraged.
Regarding the species of mosquitoes controlled, a deviation from
the literature was observed by the county biologists. Included
were Aedes sollicitans, Ae. cantator, Ae. trivittatus, Ae.
sticticus, Ae. canadensis, Culex pipiens, Cu. restuans, Cu. salinarius,
Cu. territans, Psorophora columbia, Anopheles quadrimaculatus
and An. punctipennis. The latter two are not reported in the
literature as being particularly susceptible to mosquitofish predation.
In order to address some of the operational aspects of the program,
and to encourage interaction between all agencies involved, the
production of a booklet entitled "How To Use The State Bio-Control
(Mosquitofish) Program For Mosquito Control In New Jersey"
began. This document was available to counties in 1994. The demand
for literature on the subject by members of the general public
has stimulated the authors to use excerpts from it as a one page
"fact sheet. "
All of this effort, and what has been learned from it, encourages
the members of the program to continue to investigate ways to
make it function better, consider other fish species for stocking
and examine other methods of biological control. County mosquito
control agencies which are subject to scrutiny of their integrated
control strategies, are now able to obtain an unlimited supply
of a control agent and the associated expertise as another form
of state-aid via the NJ State Mosquito Control Commission.
BIBLIOGRAPHY
Chapman, H., 1985. Biological control of mosquitoes. Amer. Mosq.
Cont. Assoc. Bulletin #6.
Gooley, B.R. and F.H. Lesser, 1977. The history of the use of
Gambusia affinis (Baird & Girard) in New Jersey. Proc. N.J.
Mosq. Cont. Assoc. 64: 154-157.
Mallars, J.L. and J.R. Fowler, 1970. Mosquito eating fishes of
California. California Mosquito Control Assoc.
New Jersey State Museum, 1907. Annual Report.
Sholdt, L.L., D.D. Ehrhardt and A.G. Michael, 1972. Guide to the
use of the mosquitofish, Gambusia affinis, for mosquito
control. Navy Environ. & Prevent. Med. Unit, 1-18.
Smith, C.M. 9 198 1. A practical small-scale fish facility for
overwintering Gambusia affinis. Proc. N.J. Mosq. Cont.
Assoc. 68: 137-139.