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Raising super walleye

Project raises all male ‘super’ walleyes at Garrison Hatchery

Rob Holm, hatchery project manager, checks to make sure a tank of young walleye are doing well. The walleye will be kept for two years inside the hatchery. Kim Fundingsland/MDN

RIVERDALE – They are raising “super” walleyes at the Garrison Dam National Fish Hatchery.

No. It’s not quite what you might imagine. These will not be gigantic fish that will overtake the record book or swallow up boats and anglers. Quite the opposite. These super walleyes will be used to help eradicate their own population.

That’s right. There are places where walleye, the most sought after fish in North Dakota, is considered an invasive species and targeted for eradication. But don’t worry North Dakota.

The super walleye at the Garrison Hatchery are not being raised for release anywhere in this state, but rather in Idaho where too many walleyes are causing unwanted problems with what has historically been an outstanding fishery for native cutthroat trout. Walleye are not native to those waters, likely having been translocated illegally, and feed heavily on young cutthroat. So much so that some species of cutthroat are considered threatened due to a combination of habitat loss and competition from non-native fish.

While the project is a first for the Garrison Hatchery, the concept is not new. It has been used in other areas of the U.S. and is a proven method of dealing with unwanted or invasive fish. Rob Holm, hatchery project manager, explains.

Kim Fundingsland/MDN These two-week old walleye will be raised on a special feed that will insure that all their offspring will be male.

“The idea is a science fiction-type story but it’s a great idea actually,” said Holm. “We’ll turn a male into a female, essentially. Keep in mind, we are not altering genetics. We are not changing the genetic make-up of fish. We are changing the sex.”

Female walleye have XX chromosomes, males XY. The newly hatched walleye in hatchery tanks will be raised on feed coated with a hormone that will determine the sex of the fish. The walleye will be raised under hatchery conditions for two years, the longest time ever for walleye in the Garrison facility.

“What you end up with chromosome-wise is YY, so anytime you would cross that male with a female it will have a Y, which is a male link,” explained Holm. “Every egg that is produced will have a Y in it, which means every egg will be a male.”

It may sound like something out of Jurassic Park, but not quite. After a two-year residence in the Garrison Hatchery the walleye will transported to Idaho and released into the wild. There they will breed with wild walleyes and thus begin the reduction of an invasive and unwanted population.

“What you end up with after a couple generations is a population that is all male,” said Holm. “It will reduce the population significantly and it will eventually die off with the life of the fish.”

Holm sees other potentially beneficial applications for so-called “super” fish.

“Think about carp, any species of carp,” said Holm. “If we had super male carp we could make a difference where carp, which is an invasive species, are not wanted. With Asian carp it would be the same opportunity, another way to manage a fishery.”

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