The use of the mosquitofish, Gambusia affinis, for rice field mosquito control at the rate of 224 g/ha (0.2 Ib/acre) did not affect the population densities of copepods, ostracods, Corixids, dragonflies, Belostomatids and aquatic beetles but did reduce the densities of cladocerans, mayflies, damselflies, Notonectids and Chironomids significantly. The reduction of insects and crustacean densities did not cause mosquito larval resurgence.