CBC News, Cory Correia, August 15, 2018 - BRITISH COLUMBIA. B.C. lake infested with hundreds of goldfish just months after pets released into wild.
Some goldfish in Pinecrest Lake are now as large as 13 centimetres, says invasive species expert. Residents of a small B.C. lakeside community say they're dealing with a goldfish infestation after someone dumped their unwanted pets in the water.
Pinecrest Lake, which is located about halfway between Squamish and Whistler, had no goldfish in its waters last year — but now they number in the hundreds, according to the Sea to Sky Invasive Species Council.
"People have been observing schools of 30 to 40 fish schooling together at a time. They vary in sizes, some small, some up to five inches [13 centimetres] big," said Clare Greenberg, the council's executive director.
Greenberg said the goldfish, the smallest member of the carp family, were released in the lake in the spring or early summer, and were likely placed in the area by well-meaning pet owners.
"We're kinda choked," said nearby resident Mary Brown. "We were like, what do we do now?"
Growing and thriving
Greenberg said residents contacted the council to investigate the infestation and what it might mean for the lake's ecosystem.
"What happens with goldfish is once they're released into a native ecosystem they really thrive, they reproduce prolifically, and they quickly dominate aquatic environments," she said.
She said the omnivore fish are bottom feeders that out-compete native fish for food and habitat, eating basically everything while disturbing sediment and increasing the turbidity of the lake.
Greenberg said goldfish are only limited by their environment, so while they may be small creatures when contained in a fishbowl, in a lake with more food they can grow to the size of a football.
"It seems that goldfish, once they establish in a lake, do really well and it's very difficult to control them once they're there," said Greenberg.
Greenberg has seen goldfish infestations throughout B.C., including White Lake near Salmon Arm, Dragon Lake near Quesnel, and Millars Pond in Whistler.
Eliminating the infestation
Greenberg said natural options to contain or eliminate the goldfish infestation are limited because predators like birds of prey don't like eating goldfish, and they're not that tasty for human consumption either.
That leaves two main options, according to Greenberg: sorting or poison.
In the first, a surveying method known as electrofishing could be used to attract and stun the lake's fish, and then selectively remove the goldfish and leave the native fish in place.
The more severe course of action is to apply a natural pesticide to the lake, called Rotenone, which effectively poisons and kills all the fish.
Greenberg said they're speaking with experts from the province about options, but a site-specific assessment will be needed to determine the best course of action.
Pinecrest Lake is located in an independent region with around 200 residents, most of whom belong to the Pinecrest Lake Stewardship Society.
The society said residents have authority over the lake and will make a decision on the possible solutions put forward by the invasive species council.
Greenberg said it's a cautionary tale for pet owners who may be considering disposing of unwanted animals in the wild. She urges them to look for alternatives.
With files from CBC's On The Coast
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