Submergent vegetation in rice fields facilitates mosquitofish but fails to reduce mosquito populations

Mosquitoes are important vectors of diseases so that predators and pathogens of mosquito larvae are widely used to reduce mosquito numbers. In rice fields, mosquitofish have been introduced around the globe to control mosquitoes and research has explored factors that contribute to their effectiveness. Rice fields harbor weeds as well as rice although the effects of submergent macrophytes has received little attention. This study evaluated the consequences of submerged naiad on mosquito control in experimental rice fields in California. Observations suggested that mosquitofish densities were greater in fields with more naiad cover. Populations of larval Culex tarsalis mosquitoes were not different in enclosures that had been seeded with naiad and those that had been seeded with rice. Anopheles freeborni mosquito larvae were more abundant in enclosures with rice early in the season and more abundant in enclosures with naiad later in the season. Mosquitofish were more common in enclosures with naiad. Sunfish are also present in rice fields and the addition of sunfish reduced mosquitofish numbers; this effect was more pronounced in enclosures without naiad, indicating that naiad may provide sone refuge for mosquitofish from sunfish predation. Mosquitofish are generalist predators, and they reduced the abundance of ostracods, small crustacea that may compete with mosquitoes. In summary, submergent vegetation is often abundant in rice fields and may act as a foundational species, determining the abundance of predatory fish and influencing the invertebrate community, including mosquitoes.