The release of mosquito fish into water courses in Guangzhou to fight dengue fever epidemic has raised concerns over intrusion by the alien species.
Guangzhou, the capital of Guangdong province, is fighting mosquito-borne dengue fever, and the city had recorded 27,400 cases of the disease this year by Monday. Guangdong had recorded 32,446 cases.
The water authority of districts in Guangzhou put a large number of mosquito fish (Gambusia affinis) into water courses in efforts to fight the epidemic, according to the Guangzhou Water Authority.
Mosquito fish, which eat mosquito larvae, have been introduced into ecosystems in many parts of the world to lower mosquito populations. However, the species can be a major pest when introduced outside their natural range, and have been known to feed on the eggs, larvae and juveniles of native fish and amphibians, according to the Washington Department of Fish and Wildlife.
The fish were also put into park lakes and ponds in Guangzhou in 2006 to control a dengue fever outbreak.
A pamphlet from the Guangzhou Aquatic and Wild Life Conservation Center lists the species as one of the most threatening alien species and unsuitable for the natural waters of Guangzhou.
Mosquito fish have replaced some fish species to become a dominant species in some low-lying waters in Guangzhou, threatening those species and affecting local salamanders and frogs, reported Southern Metropolis Daily.
A specialist in insect control said the tiger mosquito, which transmits dengue virus and prefers standing water in containers, does not live in natural water courses, adding that water courses with fish in them do not breed mosquitoes.
Peng Shaolin, director of the Institute of Ecology and Evolution of Sun Yat-sen University, said local species make a good choice for the biocontrol of mosquitoes. If alien species are involved, ecological risk assessments should be made beforehand.