SPRING MILLE LACS FISHERIES UPDATE

DOES ICE OUT AFFECT THE FISH POPULATION?

By VIVIAN LaMOORE, INAAJIMOWIN EDITOR

With record snowfall amounts across Minnesota this winter, it seemed like the snow would linger until June — at least — and the question of “when will the ice go out on Mille Lacs Lake?” has spurred many arguments and perhaps more than a fair share of side bets over the decades. With so many variables at play, one guess is about as good as another. A rapid snow melt across the state in mid-April leaving lakes void of a heavy snowpack created hope of hitting that average date of April 26. However, a return to cooler weather and more snowfall slowed down the melting of ice again, and as of the print date for this issue going into May, there is plenty of ice remaining. But it Minnesota, and a lot can change in just a matter of days.

According to records kept by the local paper, the Mille Lacs Messenger, the average ice out date for Mille Lacs Lake has been April 24, and the Minnesota DNR reports the average to be April 26. Ice outs had historically occurred with minimal variability throughout the 1980s and 90s. Beginning in 2000, with an ice out occurring on April 2, ice out dates have become much less consistent.

Since about 2008, the ice out dates have fluctuated greatly, with 2012 taking the record for earliest ice out on March 26, immediately followed by the latest on record, May 16, 2013, followed by another later than average date of May 5 for 2014. That all means the average ice out for Mille Lacs is April 26.

Local chatter from armchair biologists point to the years of 2013 and 2014 as good year classes for walleye, meaning many young of the year survived. Those were years with late ice out dates. Also, 2013 was one of the most successful hatches of walleye ever, according to Perry Bunting, who is an actual biologist with Mille Lacs Band DNR. However, he added Mille Lacs Lake was not the only lake that saw a great year class in 2013. Walleye lakes that support a sustainable fishery have, and need, a good year class every 4 to 5 years, but Mille Lacs was more in the territory of every 7 to 10 years.

Carl Klimah, Fisheries Biologist with the Mille Lacs Band DNR (also has an actual degree in biology) said there are a few theories behind a good year class associated with late ice-outs. But the theories are not supported enough by conclusive data to form a true scientific conclusion one way or the other.

Both Bunting and Klimah agreed on those theories — keep in mind, these are theories not supported by data. One theory is, the later the ice out occurs, the less chance of having a cold front come in and shut down the food chain, which is needed to feed the young fry. When it does finally start to thaw, it can happen fast; since it’s already getting warmer with a late spring, the ground can’t take in all of the run-off, and much makes it to the lake instead, carrying a lot of the nutrients with it as well, which will feed the algae and bugs [zooplanktin] in the food chain. “With the late spring in 2013, the theory I heard was that when the fry hatched, the food chain was in full gear and there was plenty for them to eat,” Bunting said. “Walleye fry only have an egg sac that will feed them for two days or so and then they need food. If there’s no bugs, they will starve.”

Klimah added it could be that a late ice out prevents zooplankton from getting eaten by zebra mussels and other species, leaving more of the zooplankton for the new baby walleyes to eat. The more of a food supply they have, the more successful a survival rate will be.

Walleyes depend on a couple of factors on when to spawn: photoperiod (length of daylight) and water temperatures. Walleyes spawn when temperatures are around 42 to 44 degrees, but with ice still on the lake, the temperature is kept low, and thus little to no spawning occurs. “If it’s a late ice out, the length of day factor is already right, and a great number of fish are just waiting to spawn, and when the water temps are right, the spawn will happen in days versus a couple of weeks as in a typical spring,” Bunting said.

The Minnesota DNR website also stated that weather will affect the success of spawning and can vary greatly year to year. “Rapidly warming water can cause eggs to hatch prematurely. Prolonged cool weather can delay and impair hatching. A cold snap after the hatch can suppress the production of microcrustaceans that walleye fry eat.”

Of course, added to the local chatter from the armchair biologists was that in 2013 with the late ice out, the tribes were unable to harvest many fish thus, more fish survived to spawn which resulted in the huge 2013-year class. “That was hard to believe, because at the time, the estimated spawning biomass was at its lowest point ever, I believe,” Bunting said. “That would mean the lowest number of mamas and papas pulled off the largest spawn ever. Like I mentioned earlier, many other lakes also had phenomenal 2013-year classes, so the lack of netting doesn’t support their theory. I think the late ice out causing the right conditions to feed the little tykes was what happened and just what the lake needed.”

Klimah points to the data and said the current data simply does not point to a direct correlation to late ice out and the survival rate of the walleye. “We just cannot conclude with a definitive scientific answer that late ice out helps the survival of the walleye.”

The good news for Band members is Mille Lacs is reporting an increase in walleye (ogaa) by 15 percent. “Juveniles are more abundant, adults are fatter, and there are more perch for food,” Klimah said.

Ogaa quota increased to a total of 175,000 pounds for state and tribes allowable harvest levels. The tribes have an allowable harvest level of 74,700 pounds of ogaa which is divided by the six tribes in the 1837 Treaty, leaving the Mille Lacs Band to harvest 21,519 pounds.

Gill netting and spearing season does not last long at Mille Lacs Lake. Once the first gill net hits the water, it's usually on between 8 to 10 days or less before the quota is used up. “On top of that, there are more netters, which seemed to have resulted from people taking it up during Covid-19 lockdowns,” Klimah said. “So, please harvest more northern pike, as our quota for pike is at 50,000 pounds.