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.