Field evaluation of Tilapia zilli (Gervais) as a biological control agent for mosquito control

Abstract Tilapia zilli (Gervais), a larvivorous fish identified in the Mwea Rice Irrigation System (Kenya), was evaluated in the field to assess its potential for biological control of mosquito larvae. The study was conducted from October 1991 to April 1992 in experimental ponds constructed at Mbui-Njeru, which is one of the 36 villages in the irrigation scheme. T. zilli was found to be extremely effective in controlling mosquito breeding that persisted throughout the study period. However, the presence of vegetation and turbidity significantly reduced its efficiency in predation. The negative effects of vegetation could be averted by combining T. zilli with an herbivorous fish to control weeds. Similarly, breeding of other larvivorous organisms, including frogs, should be encouraged to enhance mosquito control efficiency. It is suggested that positive measures should be taken to deter colonization of catfish whose presence aggravates the turbidity problem and also depletes the fish population due to its substrate feeding and carnivorous behaviour.