Unpredictable weather affects walleye and other creatures

By Mike Rahn

When we think of history-making weather, we’re likely to think of epic events: of blizzards, floods, tornadoes, hurricanes, cyclones; of dramatic rescues, disaster declarations, bold and all-caps newspaper headlines, or program interruptions for TV “breaking news.”

But history-making weather can also be about what doesn’t happen, especially when the past has told us that it should.

Before the arrival of widespread snow over much of Minnesota in the week leading up to Easter 2024, many were calling the winter of 2023-24 “the winter that wasn’t.” food and poor walleye fry survival.

And, despite the fact that this pre-Easter event dropped up to a foot of snow in some areas — snow that melted quickly with warm temperatures and April’s powerful sunlight — that “winter that wasn’t” label is still close to the truth.

From November 2023 through late March 2024, Minnesotans saw little snow and predominantly bare ground, the opposite of normal. We experienced record stretches of warm temperatures rather than our customary cold.

Rain fell instead of snow. Many lakes had ice conditions that were uncertain at best, dangerous at worst. This spring, many new records were set for early ice-outs on Minnesota lakes.

When our most recent winter is measured against history and generations-old Minnesota winter lore, it does not measure up.

Some are OK with that. During a more typical December to April, “winter haters” find themselves asking, “Why do I live here, anyway?” They prefer little or no snow, temperatures that are balmy for winter, and an early ice-out so they can get their boats back in the water as soon as possible.

Others embrace winter and look forward to the seasonal variety and recreational pursuits that depend on more typical weather. They look forward to winter’s hardy birds visiting their feeders, to stepping into cross-country skis or snowshoes for a glide or a hike, taking trail rides on a snowmobile or dropping a baited hook through the ice to walleyes or crappies suspended beneath the surface of a frozen lake.

Beyond the spectrum of our personal reactions to the changing seasons, scientists have additional perspectives. They also ponder the potential effects that changing seasonal weather patterns may have on our natural world.

In particular, the potential consequences in places that historically have had Minnesota-like climates. Some of these potential changes may be unwelcome.

It’s not about political debates over whether “climate change” is real, or about whether observed changes are caused by human activities.

It’s about measurable variations that are being recorded by scientists: thermometers recording temperatures, rain gauges measuring rainfall, depth measurements recording changing amounts of snowfall, and marking calendars with ice-on and ice-out dates.

The temperature and precipitation patterns of the fall-to-winter-to-spring cycle have survival consequences for plants and animals, from the tiniest plankton deep in a lake, to the most massive moose in a northern Minnesota boreal forest.

Each creature responds to the forces in its environment, whether they are climate-driven forces — like temperature and precipitation — or impacts from other living things that share their environment.

Together, they’re nature’s orchestra, each living component interacting with others to create harmony. If one element is changed, it will likely have an impact on the rest, just as would be the result if a composer changed the notes played by an orchestra’s violin section, or its cellists.

Each time this happens, the stage is set for a poor walleye year class and fewer catchable-size walleyes for anglers.

Not only are lake ice-out dates trending earlier, but wide variation from one year to the next has become more common, too.

For instance, on a number of central Minnesota lakes there was roughly a sixweek difference in ice-outs between spring 2023 — happening near the end of April — and spring 2024, when ice-out generally occurred in mid-March.

As should be obvious, such variations are a result of major variability in winter temperatures.

Impacts on bugs and trees

Impacts on walleye survival are not the only consequences of the milder winters that are becoming more and more common.

The result will be something other than the original. We might like the result. Or we might not.

Although no winter is an exact carbon copy of another, variations from one winter to the next — especially variations that are extreme — can disrupt nature’s harmonies. Some we might not notice. Others will hit close to home and may be all too evident.

Impacts on walleyes

One of these disruptions — based on research by the University of Wisconsin — is a mismatch in the timing of our northern lakes’ ice-outs and the spawning of walleyes, the game fish that is odds-on the most sought-after here in Minnesota.

The study found that in years of early iceout, foods that newly hatched walleye fry rely on may have already passed their peak abundance. This can contribute to high mortality of these just-born walleyes, and thus to diminished numbers when that year’s class reaches catchable size.

Walleye fry are only about one-fourth of an inch long when born and live on their yolk sac for five to eight days, after which they must find suitable size food to survive. When a lake’s ice-out happens at what might be considered the normal or optimum time, it is followed soon after by a bloom of phytoplankton, microscopic plant life.

Then the lake’s zooplankton — microscopic animal life — feed on the phytoplankton. Walleye fry, their yolk sac now consumed, begin feeding on the zooplankton as their first real meals.

That’s how it should happen. But University of Wisconsin researchers are finding that walleye spawning is not as responsive to early or variable ice-out dates as is their primary early food source, the plankton.

Researchers have found that while lakes are thawing earlier, the timing of walleye spawning may not be advancing as much as ice-out dates.

Plankton seem to respond more easily to variable ice-out dates. This can mean that by the time the walleyes spawn, the greatest abundance of phytoplankton and zooplankton may be past, resulting in a shortage of

Shorter, warmer winters provide a survival advantage to some insects that are harmful to Minnesota forests. One of these is the emerald ash borer, a tiny, iridescent green insect whose immature larvae feed beneath the bark of ash trees, severing the vein-like channels by which the trees’ roots feed the rest of the tree, eventually killing it.

Green and black ash combine to be the most abundant tree in Minnesota, and their loss would dramatically alter Minnesota’s forests and even urban landscapes.

The graceful, showy tamarack is not nearly as widely distributed or abundant in Minnesota as the ash, but is admired for the lustrous, golden tones its needles acquire before they drop in late fall. A member of the larch family, Minnesota’s tamaracks are under attack from the eastern larch beetle, which has been surviving in greater numbers due to recent milder winters.

Warmer winters and earlier spring-like weather are leading to an earlier onset of sap running in maple trees. One maple syrup processor reported that to accommodate the variability of temperatures from one winter to the next, he has to be prepared to begin tapping trees as much as six weeks earlier than his grandfather typically did.

Ticks, those tiny, blood-sucking critters that bedevil humans, our dogs and wild creatures alike, are active later in the fall and earlier in spring when winters are mild, as our most recent one has been.

Not only do they then have more opportunity to be a nuisance — and potentially infect us with such maladies as Lyme disease and anaplasmosis — but ticks when overabundant can harm native wildlife.

This includes wildlife as large and robust as moose. Ticks burrow under the moose’s dense fur, where it’s warm enough for them to survive and where they can feed on the moose throughout the winter.

In a normal winter with good snow cover, many of the eggs that will be shed by these ticks in spring will die. But when there is little snow cover, egg survival is high. This contributes to major tick outbreaks, which — through loss of blood and vital nutrients — can weaken and kill significant numbers of moose, especially their calves.

Impacts on other creatures

Some creatures, however, actually benefit from warmer winters with little snow cover. One of these is the whitetail deer. Deep snow can hamper deer movement and can eventually reduce their feeding options; this negative effect is compounded by energy-draining, subzero temperatures.

Winters like our most recent one, with little snow and warmer temperatures, are ideal for optimum deer survival.

The same can be said for farmland pheasants, which are primarily ground feeders. They can suffer significant winter mortality when snow comes early, lies deep on fields and in the cattail marshes that provide security cover, and remains well into spring.

On the other hand, Minnesota’s other popular game bird — the ruffed grouse — actually does better during winters with abundant snowfall.

One of their evolutionary adaptations is to burrow down into deep, soft snow, emerging only to feed — typically early and late in the day. While such predators as the fox might occasionally capture a grouse in these underground hideaways, grouse are essentially safe there from such avian predators as hawks or owls.

Conserving body heat in their insulated shelter, their need to feed and expose themselves to predators is also reduced, enhancing their odds of surviving the winter to breed in spring.

A mild winter such as this one, while perhaps making lower energy demands on all wildlife, can prevent grouse from optimally benefitting from their remarkable snow-roosting survival adaptation.

Earlier ice-out on lakes and wetlands can accelerate the northward migration of ducks,

Despite a mild 2023-2024 winter, a group of ice anglers were able to venture to Lake Winnibigoshish. Nancy Vogt / Echo Journal geese and other waterfowl, giving them an earlier start to nesting and rearing their young. This can be beneficial when a nest is destroyed by a predator, such as a skunk, fox or mink, giving the birds more time for a re-nesting attempt to be successful.

Not to be overlooked are the consequences of a shortened winter and an early spring for anglers. While the general fishing opener in May is unlikely to be advanced to an earlier date anytime soon, the most eager anglers are on the water in pursuit of crappies almost as soon as ice-out permits. They, too, are among the creatures affected by the seemingly greater unpredictability of our weather.

MIKE RAHN, Brainerd lakes area resident, writes Inside the Outdoors, an outdoors column published in area publications and on their websites, including the Pineandlakes Echo Journal and its website, www.pineandlakes.com.