Photo source: Rowena Burns

Case Studies - Gold Fish - Carassius auratus

The goldfish (Carassius auratus) is a highly popular aquarium and pond pet that is native to central Asia, China and Japan. Gold fish can adapt to a wide range of temperature and habitat conditions. Today, as a result of selective breeding, many different varieties exist. Because goldfish have been widely distributed through the ornamental pond and aquarium trade and through intentional and unintentional release, they can be found in many lakes, ponds, lagoons, rivers and ditches where the water is cold and slow flowing and where there is sufficient aquatic vegetation.

There is concern that the presence of growing numbers of goldfish in our waterways is increasing the occurrence of algal blooms. It is reported that their feeding methods, i.e. bottom-sucking feeding, result in increased availability of nutrients and bacteria necessary for growth of algae, thus degrading these habitats. Goldfish are also reported to increase water turbidity, deplete aquatic vegetation and, in some cases, threaten native fish species by preying on them and competing for food.

As with many other invasive aquatic species, prevention of accidental release remains the best means of controlling their spread. This can be achieved by returning or donating unwanted goldfish to a pet store, school, another hobbyist or local organization that can provide a home or find a new owner.

For more detailed information on this invasive aquatic animal, contact:

Global Invasive Species Database; www.issg.org/database.