What is the primary function of a piscicide?

A piscicide is a specific type of pesticide designed for the control or elimination of fish populations in a given area. Its primary function is to manage fish populations, often for purposes of fisheries management or the eradication of invasive species that may be detrimental to the ecosystem. By targeting fish, piscicides are utilized in various aquatic environments, such as lakes and ponds, to ensure a balanced ecosystem or to protect native fish species.

The other options refer to controls of different types of organisms: insects, birds, and toads. While these organisms may also require management in various contexts, they fall under different classifications of pesticides like insecticides, avicides, and amphibian control agents respectively, and do not pertain to the specific purpose of piscicides.