Jim Elliot/Salmon Arm Observer Two current studies are looking at White Lake’s invasive goldfish population. A third proposed study will look at how best to remove them.

White Lake part of invasive goldfish study

Rotenone treatment not suited to larger water bodies.

White Lake’s ongoing goldfish problem will be the subject of a study on how to best deal with the invasive species throughout the province.

White Lake and Little White Lake are among several water bodies in B.C. where goldfish have in some way been introduced. In the case of White Lake in the Shuswap and Dragon Lake near Quesnel, the goldfish are competing with successful pre-existing trout fisheries.

While goldfish have been an issue for White Lake since at least 2009, there is limited information on what impact they’re having on the lake and trout, and how to best deal with them.

“They have an impact – how big of an impact, we don’t know,” said Andrew Klassen, senior fish biologist with the Ministry of Forests, Lands and Natural Resource Operations.

Klassen said the goldfish population of White Lake is known to fluctuate, which adds to the difficulty in determining their impact. As for removing them, he says Rotenone, a chemical used in 2009 to eradicate invasive, illegally introduced yellow perch and smallmouth bass from Gardom Lake, is out of the question.

“In a lake like White Lake, where it’s too large for chemical treatment – using Rotenone, it’s cost prohibitive for the size, the number of residents there, I mean, that’s something that would not be considered,” said Klassen. “So other than that, there’s no real way to get rid of them. That’s the issue I guess. There’s no active plans to try and remove goldfish from White Lake.”

This is where Brian Heise comes in. Heise has been looking at the goldfish problem in White Lake for a few years now, both as a professor with the natural resource sciences department at Thompson Rivers University, and as board chair for the Invasive Species Council of B.C (ISCBC). Currently, Heise is overseeing a couple of studies on the impact invasive goldfish have on existing fisheries. He is awaiting funding approval for a third study that will look at how to remove them.

Heise agrees that Rotenone is not the answer for White Lake.

“If you Rotenone the whole lake and kill it all off, that usually works quite well, but that’s a very extreme measure and I think something like White Lake, with such a valuable trout fishery in there, you wouldn’t want to do that,” said Heise. “I think these other techniques of electroshocking or doing some select netting around the edges might work a lot better.”

One of Heise’s students is currently studying the goldfish in Dragon Lake. While the study is not yet complete, Heise says the goldfish are having an impact in that they are competing with trout for food.

“They are eating the food the trout eat,” said Heise. “They’d be bottom feeders that grub around on the bottom, and that tends to stir up the sediment and that creates dirty water or increased turbidity, which can affect the plants growing in the lake. This can affect the ability of the fish to find food, or it can even, in extreme cases, make it hard for the fish to breathe through their gills.

“But these are all, well, they’ve never been tested in British Columbia, so that’s what I’m hoping to be able to do is get a masters student looking at it in more detail so we really know what we’re talking about. It’s pretty hard to extrapolate studies done in other parts of the country or other parts of the world to our situation here in B.C. with our trout lakes.”

Heise also wants to put transmitters in some of the White Lake goldfish to learn where they’re going throughout the year, what depths, etc., addressing why they seem to be there some years and not others.

Klassen said the province supports Heise’s funding application to study how to control goldfish populations provincewide.

Speaking to their physiology when introduced into the wild, Heise says surviving goldfish tend to lose their orange/gold colour, becoming more coppery with dark brown, grey and white colouration, and that they can grow much larger than what people see in home aquariums.

“I think it’s a big myth that they really just grow to a certain size…,” said Heise. “If there’s lots of food and the right temperature, then they can get quite large, as in several pounds anyways, quite large.”

If they’re small, goldfish may be eaten by certain kinds of trout. Otherwise their only predators are wading birds.

Heise also describes goldfish as being very resilient.

“They can handle cold temperatures, they can handle ice cover, they can handle low oxygen,” said Heise. “They’re a very tough fish. They can actually operate without oxygen for awhile so they can metabolize anaerobically, and they urinate alcohol of all things. A pretty bizarre physiology.”

Wearing his ISCBC hat, Heise said there are generally two ways goldfish get into lakes – they are either introduced by people or make their way to lakes when ponds on lakeside properties are flooded.

“For me, a lot of it is about the public message too, the sole idea that we shouldn’t be releasing any of our pets that we have at home,” said Heise, “whether it’s a snake or fish or small mammal or birds, you really want to keep pets in the house and not loose because they really can cause a lot of damage once they get out there.”

Heise said he plans to be back at White Lake in the spring to continue his studies.


@SalmonArm
lachlan@saobserver.net

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