A goldfish swimming in Lost Lake, around 10 kilometres north of Terrace on July 16, 2021. (Ben Bogstie/Terrace Standard)

A goldfish swimming in Lost Lake, around 10 kilometres north of Terrace on July 16, 2021. (Ben Bogstie/Terrace Standard)

Experts warn of invasive ‘super fish’ in Terrace area waterbodies

Goldfish detected in Howe Creek, province looking into chemical treatment of Lost Lake

Last week, the Ministry of Forests, Lands, Natural Resource Operations and Rural Development, confirmed that it was looking into chemical treatment of Lost Lake to eliminate an invasive population of goldfish.

The ministry also noted that it had detected goldfish in Howe Creek — a Skeena River tributary — linked to a residential goldfish pond in Terrace.

But how big a threat to the environment can such a little fish be?

Thompson Rivers University researcher and goldfish expert Brian Heise describes them as ‘super fish.’

“I study fish and I’m a fish snob, I used to look down my nose at goldfish, I didn’t really like goldfish per se,” he said.

“Now I have tremendous respect for them, and that’s reason why I think we have to try to keep them out of our lakes and ponds and our rivers, because once they’re in there they can be quite difficult to get rid of.”

Heise said that goldfish are the only vertebrates he knows of that can handle environments with no oxygen through a special anaerobic process, producing alcohol as a byproduct. He said that goldfish have been studied surviving in conditions with little to no oxygen for up to a few months in ponds.

They also may have the ability to reproduce asexually. Heise said the phenomenon, called gynogenesis, has been documented in close relatives of goldfish like Prussian carp.

“What that term means is that a female goldfish can lay eggs, and she doesn’t need a male goldfish, doesn’t need goldfish sperm to get those eggs to start developing,” Heise said.

“What she will do is steal sperm from another species of minnow and then that sperm will then activate the egg so the eggs will start dividing and they will start developing on their own, so with asexual reproduction they’re all clones of that mother goldfish.”

Goldfish live up to the ‘super fish’ moniker when released into B.C. waterways by making the environment theirs. Goldfish grab pieces of sediment at the bottom of a lake or pond, uprooting and eating vegetation. That raises the turbidity, making it harder for light to reach other plants and making it more difficult for other species of fish to find food.

They directly compete with other fish for food and can also eat aquatic insects and plankton.

Heise said there is a lack of research about how goldfish would do in a river like the Skeena, but they would likely compete with salmon and other species.

“I can’t say we know for sure what will happen, they’ll probably be okay, they’ll survive there, they’ve been known to migrate hundreds of kilometres, for example, in river systems in Australia, so we know they can do it,” Heise said. “But whether they would thrive and produce large populations, really, that would be be speculation on my part, we don’t really know.”

“I think that the problem there is that they get they get in the Skeena and start spreading around, they might then be able to get into little tributary streams and then into other lakes in the watersheds.”

Gail Wallin, executive director of the Invasive Species Council of BC, said that if officials decide to pursue chemical treatment of Lost Lake, they would use rotenone, which targets fish but does not affect plants and breaks down in the water.

In light of goldfish being detected in Howe Creek linked to a residential goldfish pond in Terrace, Wallin said people should realize that the risk of fish reaching a natural waterway is higher than they might think.

“If you think you have a pond outside, that quote ’has them contained’ you’ve got to realize, the situation in Williams Lake was that a flood was going to spread all of those goldfish into into the Williams Lake area, or into your streams, that’s not responsible,” she said.

“Nor [is it responsible] if that osprey comes by and picks it up and drops it in the pond next door, or slips out and drops into the lake.”

As for a Lost Lake goldfish derby? Wallin said that method would not be a good way to deal with the problem, because it would be impossible to catch enough to make a difference and typically when something is made fun, it encourages more goldfish releases.

She said the the number one priority is educating people so they do not release fish and avoid a situation like Lost Lake entirely.

“The other thing that we would encourage people to do is to report, so to go through our website bcinvasives.ca,” Wallin said.

“If you think you see goldfish or anything else that’s strange, give us a report because if we’ve found them in some lakes, there’s probably a really good chance that they’re in more lakes.”

READ MORE: Province looking into possible ‘chemical treatment’ of goldfish in Terrace area lake