Mosquitofish introduced to Hawaii in 1905 now threaten native damselfly

September 6, 2026 at 07:18 PM1 min

This digest was compiled by AI from multiple sources — links to the originals are below.

Gambusia affinis, introduced to Hawaii in 1905 to control mosquitoes, became an invasive predator of native aquatic life. The endemic pinapinao damselfly has declined to 34 known populations, prompting construction of fish-free ponds on Lānaʻi.

Key Facts

In 1905, 150 Gambusia affinis were brought from Texas to Hawaii to eat mosquito larvae.
The endemic pinapinao damselfly has only 34 known populations remaining.
On Lānaʻi Island, protected ponds are being built to exclude mosquitofish and allow damselfly reintroduction.
Mosquitofish spread across Hawaiian ponds, streams, and wetlands, feeding on small aquatic animals, insect larvae, eggs, and fry of other species.

Introduction and Spread

In 1905, 150 mosquitofish (Gambusia affinis) were transported from Texas to Hawaii to control mosquito larvae. The fish rapidly multiplied and spread into ponds, streams, and wetlands across the Hawaiian islands. They began consuming not only mosquito larvae but also small aquatic organisms, insect larvae, eggs, and the young of other species.

Impact on Native Damselfly

The endemic pinapinao damselfly, whose larvae live in water, became easy prey for mosquitofish. Once widespread in Hawaiian wetlands, the species now has only 34 known populations. Wetland loss and habitat degradation, along with fish predation, contributed to the decline.

Conservation Efforts

On Lānaʻi Island, workers are constructing protected ponds that mosquitofish cannot enter. The goal is to create safe areas where damselflies can repopulate. Measures are being taken to prevent fish access while reintroducing damselflies to these waters.