By Jill Sperling

Goldfish threatening native fish species in B.C. Interior

Dec 12, 2017 | 3:12 PM

KAMLOOPS — The Invasive Species Council of BC is reminding pet owners to be responsible when their animals are no longer wanted.

Exotic animals such as Koi carp, the European rabbit, and the American Bullfrog are considered invasive when released into the wild. One species that is especially damaging is goldfish. 

While they make excellent pets, goldfish threaten native eco-systems when introduced into B.C. lakes. 

“In B.C. lakes goldfish create a problem because they compete with our native fish for food,” explained Brian Heise, chair of the Invasive Species Council of BC. 

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Goldfish are omnivores, meaning they will eat both plants and other animals, and they will grow according to the size of water body they are placed in. 

With no natural predators goldfish pose a risk to native fish species in the B.C. Interior. 

“We have a local population in White Lake and Little White Lake, which is located close to Salmon Arm, and there they are a threat to a very famous trout fishery in that lake,” Heise said. “As a result, I think the goldfish are a concern. Some of my students at Thompson Rivers University and myself are doing research on that, and we’re finding that they are competing with the trout for food, and so they’re something that we’d like to examine ways of eradicating if we can.”

Goldfish are also causing problems at Dragon Lake east of Quesnel. 

How do the goldfish end up in B.C. lakes? 

According to the Invasive Species Council the fish are either placed there by well-intentioned pet owners, or they are carried out of outdoor ponds by spring flooding. 

“Whether it’s goldfish or red slider turtles, those are all examples of where people can make a big difference,” said Gail Wallin, executive director of the Invasive Species Council of BC. “We’re having problems with those being released in the environment, because people are putting them out there, so people are the solution. By not releasing them out into the environment, and taking them back to a friend or to the pet store that you got them from is a much better approach than releasing them into our lakes and streams.”

Once goldfish, and other invasive species, have made their way into the wild they can be difficult to eradicate. 

“There are two basic approaches, one is to kill off all the fish in the lake, and this has been done for some smaller lakes, for example in the Kamloops region,” Heise said. “Rotenone is a naturally occurring chemical, it’s found in the roots of plants in South America, and it can be used to kill off all of the fish in a lake.” 

The less dramatic, and less effective option, is to attempt to reduce the population by means of electrofishing or netting.

“It’s impossible to get them all unless you poison the whole lake, so again, even more reason to not let them in there in the first place,” Heise said.

While there is provincial legislation against moving fish like perch or bass from one lake to another, goldfish have yet to be included.