Heeding nature's call with a one-lake study and more

NEAR WALKER, MINN. – Dallas Hudson might be the most interesting man in Minnesota. Maybe the world.

I was thinking about this the other day as I watched Hudson and a researcher-in-common, Bruce Carlson, measure northern pike they caught in a trap net on a small private lake surrounded only by four landowners, one of whom is Hudson.

I first wrote about Hudson a year or so ago. He grew up fishing the 160-acre lake that once was home to good-sized northerns, fat bluegills and even some eater walleyes.

"When I was a kid we kept pretty much everything we caught," Hudson said. "We speared the lake, too."

Hudson believes the excessive harvests helped stunt the lake's fish.

So about 20 years ago, he and his neighbors made a decision. They would continue to fish the lake. But they would keep only an occasional meal's worth of small crappies or bluegills.

And no northern pike.

Credit Hudson's interest in the natural order of things for the idea.

In springtime he keeps highly detailed journals that chronicle when leatherwood blooms, also hepatica, hazel flower, red maple, dandelions, wild strawberries and chokecherries, bellwort and violets, among other plants.

"I mark the dates of first bloom, then follow through with the entire cycles," Hudson said, "first bloom followed by full bloom, then by peak bloom and on down again to full bloom and bloom."

Hudson works for the U.S. Geological Survey, gathering weather, water and other data near his home for study by scientists based as far away as Denver.

His passion for phenology — the study of seasonal natural phenomena — aides this work, and also helps satisfy his naturally curious bent.

This would allow them to collect data that would tell them, over time, how fast northerns grow and how vulnerable to angling pressure northern pike are.

"If you read the old accounts of fishing in Minnesota lakes, there were a lot of big fish," Hudson said. "That was before everyone started fishing these waters so hard and keeping nearly everything they caught.

"So I asked myself: 'Could the lake I live on be returned to one that produced many more big fish — mainly northerns — if most fish in the lake weren't harvested? And if so, how long would it take?' "

A limited harvest strategy also would help grow the average size of the lake's bluegills and crappies, Hudson thought.

But he wasn't sure.

For the past seven years, operating under a DNR permit, Hudson, aided by Carlson and another friend, Steve Bayman, has netted northern pike in spring from their study lake.

On a recent day, beneath a blue sky, Hudson and Carlson checked their spring's nets for the second-to-last time. In them they found big northerns — many longer than 30 inches, and plump — and also fat bluegills.

"Spring is when we net because it's the only time we can tell the difference between the sexes of northern pike," Hudson said. "The females have eggs, the males milt."

Hudson's study has confirmed that northerns are highly vulnerable to angling pressure.

In winter, for example, Hudson, Bayman and others regularly fish the lake using tip-ups and minnows. Their intent is to catch and measure northerns before releasing them, identifying each by its tag (or tagging a fish if it's untagged).

The remaining 90? They had been caught and released an amazing 431 times.

Additionally, of the 97 northerns, 24 measured 30 inches or longer, and each had been caught about seven times.

Upshot: If you want big northerns, these fish have to be protected over a long period of time.

"A northern in our lake — and our lake is fertile — will take six years to reach 24 inches and nine years to reach 30 inches and weigh 7 or 8 pounds," Hudson said.

A basic tenet of fisheries management is that a given lake can produce only so much "biomass," whether in the form of many little fish or relatively fewer larger fish.

"We have good numbers of forage fish in the lake for northerns, such as tullibees, perch, shiners, bluegills, crappies and bass," Hudson said. "But their abundance, year to year, can vary and affect the size and numbers of predator fish such as northerns."

Still, Hudson's study lake seems to be rebalancing the size structure of its fish in favor of bigger northerns, as well as bluegills and crappies.

In 2009, for example, 4 percent of northerns caught and netted in the lake were shorter than 16 inches, and 81 percent measured 16 to 24 inches.

By 2014, 3 percent were shorter than 16 inches, and 73 percent were in the 16- to 24-inch range.

Assuming this trend is replicable in other lakes, and assuming also that Minnesota anglers are serious when they say they want more of their lakes to be inhabited with more big northerns, the challenge for the DNR will be to find a way to induce anglers to keep smaller northerns but let the bigger ones go.

Or so believes the most interesting guy in Minnesota.

• • •

Here are some of Hudson's wildlife observations in the Walker-Akeley area, in which he compares what he sees now to what he saw in the area as a kid. (Hudson's age is 50.)

• Snowshoe hares once were "thick," now they're rare.

• Jackrabbits were sometimes seen, now they're not.

• Geese are "everywhere."

• Deer numbers are up.

• Wild turkeys now inhabit the area (Hudson killed one Friday morning with the black-powder shotgun he made in high school shop). Turkeys, Hudson said, couldn't even be imagined in the area when he was young.

• Evening grosbeaks once visited his bird feeders by the hundreds. "I haven't seen one in two years," he said.

• Bobcats are fairly common now and weren't before.

• Gray fox were nonexistent. "Now some trappers get as many grays as reds."

• Butterflies are up. "Last year was one of the highest numbers of butterflies I've recorded."

• Finally: "Development, unfortunately, is everywhere."

Dennis Anderson danderson@startribune.com