Some species of plants have roots or bark containing latex that can asphyxiate or kill fish. Batek sometimes poison fish in small streams with these substances. Here some women are pounding poisonous tree bark (species unknown) and then wringing the poison out in the water. They will simply pick up the fish that float to the surface.
Endicott Image Collection
Fishing -- Malaysia -- Kelantan., Batek (Malaysian people) -- Food., Lebir River (Malay)