Imported by the local government to control mosquitoes, along with its relative, G. affinis. Recorded from the Coamo and Patillas Reservoirs, and the Cayey River, from 1924 to 1948. A breeding population was observed at the Dos Bocas Reservoir in 2007. Established since 1924-2007. The eastern mosquitofish is a voracious predator of insects and other small fish or fish fry. Its effectiveness as a mosquito biocontrol is unknown, and it is feared that it may reduce native fishes’ populations by predating their fry or larvae (Felix Grana, pers. comm.).