Environmental experts are requesting that those who keep goldfish look after then until the fish die, rather than releasing the fish into public waterways. This is because, in countries like the U.S., goldfish are an invasive species. Such is the extent of the practice that goldfish are having a negative impact on the natural ecosystem.
Goldfish are very efficient at adapting to new environments. The practice of releasing goldfish into ponds or streams invariably leads to the goldfish becoming the dominant species, Popular Science reports. The fish can grow to a very large size (a typical size of a wild goldfish is 2 kilograms) and they can also multiply readily, which can lead to a food shortage of the fish naturally expected to be present in the waterway. This leads to an imbalance of the aquatic ecosystem.
Goldfish can also be predatory and they will eat the eggs of other fish, which again affects the balance of fish varieties through a reduction in the reproduction rate of indigenous fish. Furthermore, according to Laboratory Roots, wild goldfish behave much like carp, stirring up the natural sediments that make up the floor of a body of water as they swim close to it. The net result of this is to contaminate the surrounding water in the process. This makes it harder for native fish to survive.
In a recent interview, Dr. Sara Thompson, Lake Erie Unit Manager for the Michigan DNR fisheries division expands on this, noting: “It means they’re taking up all of the resources of fish that should be there. Only one or two native fish were found in that stretch.” DNR has had to remove hundreds of pounds of goldfish from waterways. In the Michigan state alone there could be up to 8,000 goldfish weighing as much as 450 pounds in major water sources.
Based on this the conservationist is calling on stricter laws to be in place to stop the dumping of pet goldfish into common waterways.
Many of the risks of releasing goldfish are described in the journal Ecology of Freshwater Fish. The article is titled “First evidence of spawning migration by goldfish (Carassius auratus); implications for control of a globally invasive species.”
