The involvement of aquatic plants in spawning behaviour was examined in goldfish (Carassius auratus) and crucian carp (Carassius auratus subsp.) in order to obtain basic information for environmental conservation. Spawning behaviour of goldfish and crucian carp was induced by injection of prostaglandin to females in glass tanks provided with artificial aquatic plants. Both goldfish and crucian carp actively performed spawning behaviour towards the aquatic plants, whereas frequency of spawning behaviour decreased when the plants were removed. When the plants were replaced in the tank, both goldfish and crucian carp showed spawning behaviour as actively as before their removal. These results indicate that the removal of aquatic plants largely suppresses the spawning behaviour of goldfish and crucian carp, but did not affect their spawning behaviour capacity. Such suppression of reproductive activity could happen in the natural environment where plants are reduced by construction of artificial riverbanks and lakefronts.