In 1905, Hawaii introduced mosquitofish to control mosquitoes; the tiny fish later became linked to declines of native damselflies and other threatened species

Introduced to Hawaii in 1905 to control disease-carrying mosquitoes, the eastern mosquitofish (Gambusia affinis) has caused major declines in native aquatic insects, including several threatened species of Hawaiian damselflies. Conservation reports from the United States Fish and Wildlife Service (USFWS) show that the small, non-native fish has had a serious impact on Hawaii's freshwater ecosystems because of its aggressive and flexible feeding habits. The fish was originally brought from the southeastern United States during a period of agricultural expansion. It was then widely released into streams, drainage ditches and taro fields. Instead of eating only mosquito larvae, however, mosquitofish began feeding on many types of native aquatic animals. This changed local food webs and reduced populations of native species.

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