Alien Mosquitofish

* The July 22 photo essay “Guppy Love” did not tell the whole story about mosquitofish (Gambusia affinis) in Southern California. Mosquitofish do not occur naturally in this region. They were introduced from the southeastern United States and Mexico.

Research results published by scientists at Pepperdine University have shown that predation by these alien mosquitofish has caused significant declines in native California newt (Taricha torosa) populations in the Santa Monica Mountains. According to the research, mosquitofish eat very large numbers of immature newt larvae. The newt’s defenses against native predators do not seem to be effective against the alien mosquitofish.

Widespread destruction of streams and wetlands in Southern California means that habitat for California newts and other riparian species is far less than it once was. Native animals in the few remaining aquatic habitats should be protected from extinction by these voracious alien predators. Moreover, natural streams and wetlands are habitats for a diversity of native mosquito-eating animals. Therefore, it is unnecessary to introduce alien fish into natural areas for mosquito control.

Mosquitofish do control mosquitoes, some of which are disease vectors. Therefore, it is a good idea to put mosquitofish into backyard lily ponds and fountains. It should be made clear, however, that these alien fish should be kept out of natural aquatic systems because they are ecologically harmful.

PAULA M. SCHIFFMAN

Cal State Northridge

Associate Professor of Biology

Mission Hills