The effect of mosquito control by the use of the mosquito fish, Gambusia affinis, in urban area, Tokushima, Japan

Abstract

The mosquito fish, G. affinis (Baird and Girard) was introduced into Tokushima city [Japan] in 1968 to control mosquito larvae in salt marshes and drains. The fish propagated and spread into a wide area of the city. It was clarified how extensively they distributed after 8 yr. Distribution of G. affinis in the winter was limited. During several yr following introduction, the fish were spread by members of this laboratory. In the autumn of 1975, G. affinis distributed itself to approximately 70% of the water bodies. Larvae of Culex pipiens pallens was distributed in limited places. Effectiveness of G. affinis on the control of mosquito larvae was studied by releasing fish into drains where C. pipiens pallens larvae were present. An average of 250 individuals of G. affinis/drain were released and the number of mosquito larvae decreased at 7 drains out of 9. The fish settled and were observed 4 mo. late. Effectiveness of G. affinis on mosquito control was studied by examining the number of adult mosquitoes. Light traps were set up at the G. affinis densely inhabited area and the area with no G. affinis. Comparison of the number of mosquito between the 2 areas indicated no significant difference. Mosquitoes were not abundant even in the area where no G. affinis were inhabiting.