Indirect effects of the mosquitofish Gambusia affinis on the mosquito Culex tarsalis

Culex tarsalis Coquillet larvae developed faster and had a higher survival rate from first instar to pupae in rice field enclosures that contained mosquitofish ( Gambusia affinis Baird and Girard) than in enclosures that did not contain any fish. The mosquito immatures were in predator‐exclusion cages within the enclosures which protected them from predation by mosquitofish but subjected them to indirect changes caused by mosquitofish. Mosquitofish reduced Cladocera populations to low levels in these enclosures. The results suggest that, in the absence of fish, cladocerans may compete with mosquito larvae in at least some rice fields and may affect mosquito population dynamics.