Piscicdes chemicals that are used to kill undesirable fish species in a water body for aquaculture purposes. In the past the fish farmers used to apply a wide variety of chemicals as poisons to control undesirable fishes. Such poisons even included chlorinated hydrocarbons and organophosphorus insecticides. Most pesticides have residual effects. Moreover, these not only kill the target species but also eliminate the beneficial other aquatic organisms, which is undesirable. Some alkaloids (plant products) have been found to be more effective as piscicides and less hazardous to aquatic ecosystem.
The antibiotic Antimycin-A is proved to be very effective fish toxicant and is used as piscicide. However, the piscicides of plant origin is suggested for the removal of undesirable fishes from ponds as it is relatively harmless to non-target organisms. It is known that plants of the families Meliaceae, Rutaceae, Asteraceae, Labiatae, and Canellaceae have piscicidal properties.
The plant-extract known as rotenone is widely used as piscicide by fish farmers of Asia, Europe, Australia, and USA. Generally, rotenone is present in about 68 species of Leguminous plants. Two species of Derris contain 5-9% of rotenone and several species of Lonchocarpus contain 8-11% rotenone. Rotenone has high power of killing the predatory and weed fishes. In Bangladesh, the tribal people of Chittagong Hill Tracts and Mymensingh use the root of Derris for catching fishes in shallow water.
Nicotine and related compounds occur in certain members of the Solanaceae, particularly present in the genus Nicotiana have also fish killing properties. Nicotine appears to be superior to rotenone as it is homogeneously dispersed in water, harmless to plankton detoxifies rapidly and easy to handle. Nicotine extract can be used for partial or complete control of predatory or undesirable fishes.
Some locally available plants that have piscicidal properties include Derris scandens, D. elliptica, Thevetio peruviana, Sapium indicum, Tephrosia purpurea, Euphorbia nerifolia, Mesua ferrea, Barringtonia acutangula, Azadirachta indica, Albizzia procera, Swietenia mahagoni, Acacia catechu, and Camellia sinensis. [Abdul Maleque Bhouyain]
See also insecticide.