The artificial incubation of lake trout eggs in their natural environment to help turn around depleted stocks should not be considered at this time, says Environment Yukon biologist Oliver Barker.

Barker said this week the available science doesn’t support in-lake incubation as a viable aid to help rebuild stocks.

When it comes to rebuilding lake trout populations depleted by overfishing, science says the best method is to stop overfishing, he said.

Barker said he recommended earlier this month that the Yukon Fish and Wildlife Management Board not pursue in-lake incubation as a method to rebuild stocks in lakes that are in trouble.

“It is probably not the tool for the job if you are trying to increase the population of lake trout,” he said.

NDP Environment critic Kate White raised concerns in the legislature earlier this month regarding information she had indicating the government had already gone ahead with an incubation project last summer.

The Yukon, she pointed out to the legislature, has a policy of only stocking lakes that are land-locked, with no creeks or streams connecting them to other water bodies.

White wanted to know whether the Yukon indeed contravened its own policy by conducting a pilot project in an open lake, and where the lake trout eggs came from.

Environment Minister Wade Istchenko assured White there had been no change in policy, that the government was not doing any artificial stocking in open lakes.

Barker suspects the information White was referring to regarded work commissioned last summer by the wildlife management board and its wildlife enhancement trust.

The board is seeking additional methods to bolster lake trout stocks other than increasing restrictions on anglers, he pointed out.

Barker said the options discussed included in-lake incubation using eggs and milt taken from lake trout in the same lake.

As a starting point, the enhancement trust provided EDI Environmental Dynamics with funding to identify spawning areas this past summer in lakes where stocks are in trouble, he pointed out.

Barker said he suspects that’s the work the NDP critic had heard about.

There was no incubation, and there’s been no change of government policy that says artificial enhancement will only occur in land-locked lakes, he said.

White said this week she’s happy to learn there was no actual incubation, though it may have been easier for the Environment minister to say so directly.

Barker said he recommended to the Yukon Fish and Wildlife Management Board – which is the same body that manages the enhancement trust – that in-lake incubation should not be pursued as a tool to rebuild stocks.

The potential risks, the biologist said, outweigh the benefits.

Graham Van Tighem, the board’s executive director, said this week it wants to explore more methods of lake trout restoration other than increasing restrictions on angling.

In-lake incubation and Barker’s recommendation not to pursue it is scheduled for further discussion at the board’s next meeting.

Environment Yukon was concerned that overfishing was hurting trout populations in Snafu, Tarfu, Pine and Louise (Jackson) lakes.

Consequently, more angling restrictions were put in place this year following a review by the wildlife management board.

Environment Yukon is currently asking the management board to recommend more restrictions for Fox, Kusawa, Twin and Frenchman lakes because overfishing is hurting the lake trout stocks.

The method of in-lake incubation involves capturing adult male and female trout to obtain milt and eggs, then releasing the fish.

The eggs are fertilized with the milt, then put in a protective container which is placed on the lake bottom.

The container protects the eggs from predation to maximize survival and has holes large enough to let the fry escape after they hatch.

The Yukon’s fish biologist said there are just too many unknowns about the actual success of in-lake incubation, beginning with the inability to measure success.

For instance, said Barker, there’s no ability to mark the fish, as is done with hatchery salmon when their adipose fin is clipped before the fish are released.

Without any ability to tell which fish are natural and which fish are the product of artificial in-lake incubation, he said, there are no means of measuring the success.

There are also no means of determining how the in-lake incubation will affect the natural composition of the lake trout stock, whether it will distort the age classes or overpower the genetic makeup with an abundance of lake trout from one spawning area, he said.

Baker said lake trout are faithful to their spawning areas. Offspring will use the same spawning areas, he added, just like salmon will return to the same creeks and streams where they were spawned.

Enhancing productivity of spawning site A over spawning sites B, C, and D in the same lake may upset the natural balance, he suggested.

The biologist also pointed out catching and releasing adults to provide the milt and eggs may be harder on the adult population than any benefits realized from an incubation program.

Not only is there additional stress on the fish caught to provide milt and eggs, but just being in the shallow spawning areas with boats and nets during a sensitive time could be a detriment, he said.

“There are a lot of serious questions that have to be answered before anyone gets their feet wet,” he said.

Baker said lake trout populations are affected by two factors: environmental conditions and harvest rates.

In the Yukon, he said, the lake trout habitat is great.

“Where there is trouble, address the harvest and let the lake trout population deal with it naturally,” Baker suggested.

He said his recommendation to the management board not to pursue in-lake incubation is only a recommendation.

It also comes with a suggestion that if the board wants to pursue the matter further, it should look deeper into the science and enlist the input of experts in the field, he said.

Baker said in-lake incubation of lake trout has been tried in the Great Lakes by the State of Michigan, but no more.

It was used on one lake in B.C. where a local trout population was facing extinction, but only after an exhaustive exercise to bend the provincial policy of no stocking lake trout where wild populations exist, he explained.

Barker said other than a handful of unique examples, in-lake incubation has not been used, and its success is not tried and true.

Other options to assist troubled trout stocks include educating anglers about the benefits of targeting other species, such as whitefish and northern pike, he said.

Baker said whitefish put up a fight, are good eating, and are plentiful. Where there are lake trout, there are whitefish, he said.

“I’d rather eat whitefish myself.”

Continuing to stock isolated pothole lakes is a surefire method of assisting lake trout stocks by providing alternatives for anglers, Barker said.

As the result of the Yukon’s stocking program, for instance, Scout Lake has some very large rainbow trout, he said.