Piscicides are fish poisons.

They are sometimes used in commercial fish hatcheries or stocked bodies of water when an undesirable type of fish takes over and becomes the dominant species. The fish life in a given body of water may be completely or partially killed off by wildlife managers in order to eliminate an invasive pest fish species and to allow for native species restoration. This has been needed historically many times in the US. Ruffe threaten Lake Superior. Northern Snakeheads threaten the Patuxent River watershed. Carp threaten wetlands in Idaho. The Round Goby threatens the Mississippi River.

Historically plants with piscicidal properties have been used to bring fish to the surface of the water and make them easier to catch. In the US, rotenonee’s use is restricted if the fish are to be taken for food. Most plant-based piscicides do not harm mammals; instead they damage the gills of fish. Piscicides may be used to kill predators of commercially grown shellfish. Other plant based piscicides include mullein, many legumes, Abuta, chrysanthemums (the source of Pyrethrum) and rotenone (obtained from the derris root). Some non-plant based piscicides also exist such as Antimycin.