Eastern Mosquitofish - Environmental Impact

Environmental Impact

Since G. holbrooki is not considered endangered or threatened, no true management plan is in effect for this species within the United States. In fact, this fish is considered an invasive species in Australia, due to its ability to thrive in many different environmental conditions which are usually lethal to other fish species. The main recommendation for this species is to find a way to decrease their numbers in areas where they are considered an invasive species. In Australia, they have been introduced as a means to control the mosquito population. However, they have become an invasive species that causes harm to native species which have an aquatic larval stage. Australia has set up conservation management plans to try to save native species from Gambusia holbrooki. One such management plan included releasing a chemical known to kill mosquito larvae. The chemicals used were found to have a strong effect on the G. holbrooki, but they became tolerant to most of them fairly rapidly unless amounts considered unsafe for native species were used. Another tried and failed attempt to decrease this invasive species was electrifying a lake known to have been invaded. The cost and loss of native fish was so great, this method was dropped. The main reason it failed was these fish stay in the shallows, which receive the smallest charge from the electrification method used. Later tests also revealed this species has a high tolerance for electrical shock, but the exact mechanism that allows this still seems to be questionable. Eastern mosquitofish were introduced to control mosquitoes, when in reality various small Australian native fish were already keeping mosquitoes to a minimal level. They are aggressive, fin-nipping harassers of other fish, and pose a serious threat to native Australian fish and aquatic fauna. Negative impacts on rainbowfish species and at least one frog species have been documented. Several rainbowfish populations appear to have become extinct due to the impacts of introduced Gambusia.