NORTH DAKOTA OUTDOORS MAGAZINE

Rebounding from Winter

Ron Wilson

Some fish die every winter.

It happens.

Even so, last winter was a different story. Snow came early and often and seemingly hung around forever, blocking sunlight from penetrating the ice and handcuffing underwater plants from producing oxygen fish need to survive.

The fallout, it is suspected, that more lakes than typical suffered winterkill.

A lot more.

North Dakota Game and Fish Department fisheries biologists took dissolved oxygen level readings on many lakes in the dead of winter and the findings were, not surprisingly, discouraging.

“I think our guys compiled a list that probably included 80 or 90 lakes that had concerning oxygen levels,” said Scott Gangl, Department fisheries management section leader, in early May when some lakes around the state were still iced over and had yet to reveal the outcome of the long winter. “And by concerning, it means it may not be 100% lethal, but with a lot of winter remaining, there was probably going to be a drop to lethal levels. Some of the lakes were already dead when they were tested in February.”

Yet, not all the lakes on the too-long list will likely suffer total winterkill. Some may suffer some mortality, but still pull through.

“Out of that list of lakes, I bet there’s maybe a half a dozen that were good quality lakes that don’t usually winterkill. Some of the others are marginal lakes that are kind of susceptible to winterkill from time to time anyway,” Gangl said.

“Some will winterkill every few years, some will winterkill occasionally. There really aren’t a lot of surprises on the list. It’s just that this winter triggered all of them to be low all at once because of the long-term snowpack and ice cover.”

While some of the lakes had low enough dissolved oxygen levels to kill fish, there’s a chance not everything in the lakes will die and what remains can pose management problems.

Perch in a net

“What you end up with is some of the sensitive species, which tend to be game fish or desirable fish to anglers, are the ones that are going to be impacted. Often, the survivors are the tougher species, which tend to be the nongame fish like bullheads, carp and suckers,” Gangl said. “And so, you end up with a situation where they’re now allowed to thrive in this open environment, while we’re trying to establish game fish back into a lake. That’s why we do have some problems with bullheads and other rough fish in some of parts of the state.”

Gangl said that while it’s a setback to lose dozens of lakes to winterkill, but not surprising considering the magnitude of the winter, fisheries managers are prepared to deal with the aftermath.

“Again, the vast majority of the lakes that we’re monitoring have winterkilled in the past, and a lot of them are already on our stocking request because we stock them annually,” he said. “We’re going to lose some lakes, but if you can start over with a clean slate and get a complete kill on some of these places, we’re able to restock. We’ll get fish in there as soon as we can.”

Not all of the fish will come from the hatchery to reboot winterkill lakes. Gangl said Department fisheries personnel will trap adult fish in one lake and transport them to another.

Fisheries biologist holding perch above fish holding tank on boat

“What we’ve found is that if you have a situation where you don’t have fish in a lake, call it a barren lake, we can stock pre-spawn fish like yellow perch, bluegills and crappies,” Gangl said. “If it’s something that’ll reproduce, it doesn’t take very many parents to produce a year-class in a situation where there’s no other fish in there to compete with or to eat the young-of-the-year, so they’ll take off pretty quickly.”

Gangl said it could take fisheries biologists weeks in some cases to assess the damage. Due to the late start to spring, and the significant effort required to spawn northern pike and walleye right after ice-out, getting to many of these lakes will take time.

“Our crews are so busy at this time of year, and it’s compressed in such a short amount of time. I know that there have been a handful of winterkill assessments, but on a year like this, I don’t expect most of the information to be collected until well into summer,” he said. “Again, because many of these lakes were already scheduled to be stocked, we’ll likely go ahead and do that.

“When we do our standard fish sampling from the end of May into July is when a lot of these assessments are probably going to happen this year just because of the time factor,” he added. “We just won’t have time to get to all of them right away. But over the course of summer, we’ll get to them when we normally would sample them and just to see what’s left.”

If every fishery on the winterkill lake is toast, and that’s not likely, the fishing outlook remains solid, considering that North Dakota harbors a record number of waters.

“Even if we lost all of the waters that we were concerned about, we’d still have more lakes than we had 20 years ago,” Gangl said. “A lot of those lakes are going to have really good fishing opportunities. And some of the lakes that are on our list of concern are still going to have good fishing opportunities because they’re not going to be complete winterkills.”

And those waters that will need some help from stocking and the transportation of adult fish will be back online in a few short years, Gangl said.

“One of the nice things about living in North Dakota is that our lakes are very productive, and fish grow really fast in many of them,” he said. “Also, with the snowpack, with the long winter, we didn’t see as much runoff as we kind of expected. But there was some and I think some of these lakes got maybe a little shot of water or at least the aquifers were recharged. And that will help with productivity and growth.”

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