A mistake from 1905 – how the fight against mosquitoes turned into a disaster

In 1905, the Gambusia fish was introduced to Hawaii to combat malaria-carrying mosquitoes. The predator began decimating local fauna, pushing endemic dragonflies, shrimp, and gobies to the brink of extinction, leading to uncontrolled algae growth.

In 1905, the tiny Gambusia fish from the southeastern United States was introduced to the Hawaiian Islands. It was intended as a biological weapon against malaria mosquitoes, but the experiment turned into an ecological disaster. During the agricultural boom, the fish were mass-released into drainage networks, streams, and rice paddies. Gambusia's appetite proved broader than insect larvae: the predator began wiping out almost all small creatures. The endemic Hawaiian dragonflies of the Megalagrion family suffered the most, unprepared for attacks by the agile fish. The U.S. Fish and Wildlife Service classified Gambusia as a species with the highest ecological risk. On the islands of Oahu, Molokai, Maui, and Hawaii, two unique dragonfly varieties are on the brink of extinction. Endemic shrimp and oopu gobies were also hit, their decline triggering uncontrolled algae growth. Controlling the population is difficult due to reproductive traits: females give birth to live fry, so a single fertilized individual can start a new colony. Chemical use is impossible due to threats to other inhabitants, and netting the fish in stream networks is unrealistic. Conservationists are forced to focus on protecting isolated highland areas where waterfalls serve as barriers.