Why is Gambusia affinis not used in Maryland for mosquito control?

• A. Because it is ineffective at controlling mosquitoes.
• B. Because it is native to Maryland.
• C. Because it is regulated by federal law.
• D. Because Gambusia affinis is not native to Maryland and cannot be used; Gambusia holbrooki is native and equally effective.

Answer: (D)

The key idea is that mosquito-control organisms must be chosen with ecological and regulatory compatibility in mind. Gambusia affinis is not native to Maryland, so releasing it could disrupt local aquatic ecosystems by competing with or displacing native fish and altering food webs. Because of these potential ecological risks, Maryland restricts or discourages its use. On the other hand, Gambusia holbrooki is native to Maryland and can provide similar mosquito larval control in appropriate habitats, so it is the preferred, permissible option. Therefore, the reason Gambusia affinis isn’t used is its non-native status and the ecological/regulatory implications that come with introducing non-native species.