|image courtesy of Sommai at |
Many years ago, I had a friend who built a pond in her back yard, and then bought a few gold fish to put in it. In the beginning, the fish were brought indoors during the winter months and put into an aquarium in the living room. Goldfish grow according to how much space they have and soon the fish that lived in the pond during the summer were too big to all fit into the aquarium. She would then select a few for her winter amusement, to live in the aquarium, and bought a child's wading pool for the rest of them. Those ones got to live in that pool in the basement, and by spring had usually managed to reproduce. Now, some of the offspring were pretty and golden and got to live in the pond or the aquarium, while others were brown and deemed by my friend to be "river fish". She would take those ones down and turn them loose in the Rideau River, where they may have been eaten up by larger fish.....or not. If not, then they have had ample room to grow and become an invasive species here too.
I'm not sure anyone would notice though as goldfish are carp. The common carp (Cyprinus carpio)has been found throughout the Rideau River since the 1930s. They were introduced into Ontario from the United States in 1880. This species, native to Europe and Asia, quickly spread throughout southern Ontario and has reached as far north as Sturgeon Bay, Ontario.
This fish has been blamed for destroying the spawning areas of many aquatic insects, amphibians and other fish by rooting in the mud along shorelines. Uprooting aquatic plants increases the turbidity, which is rather like smoke in the water. The suspended particles can block the grills of other fish, so they stay away. If eggs have already been laid in these areas, they could be covered by these particles, which would interfere in their development.
There have been years when I have seen carp swim up to the dam here in town. They were fascinating to watch as they made like salmon, trying to jump up the onrushing flow of the water going over the dam. I don't think there is any way any of them could have gone upstream from that point, but they surely could go downstream. I don't know if the carp I've seen here had anything to do with the "river fish" my friend turned loose all those years ago. I now suspect they fit right in with the rest of the carp in the river though.
I have also seen schools of carp in the Tay River in Perth, Ontario. The Tay is a tributary to the Rideau River, upstream from here. Children like to get into the stream that runs though Stewart Park in Perth, in the spring and pet the fish. Carp are rather docile and friendly enough to swim right up to a person. That may be why they were domesticated in the first place.
While it's likely the giant goldfish in Alberta will upset the aquatic eco system, the list of native species found in the Rideau now includes the carp. When something has been around long enough, I guess it's considered normal.
It is illegal to transfer fish from one body of water to another. That means you cannot legally do what my friend did. Not only does such an act introduce a fish into waters where it does not belong, but if you also dump the water the fish has been living in into the river too that would also introducing bacteria and parasites to a new location as well. Do not be responsible for upsetting the balance of nature, even if it's already been done in your area.
Don't flush your unwanted live fish down the toilet either. If you no longer want your finned pets, give them away, take them to a pet store, donate them to a school, or talk to a veterinarian about humane disposal.