Probing the depths of Lake of the Woods
WARROAD, Minn.—Lake of the Woods stretched out like a vast, gray sea on this weekend September morning as a fisheries crew from the Minnesota Department of Natural Resources left the dock in a 25-foot Boston Whaler to check their nets.
A stiff northwest wind had stirred up waves that definitely fell into the "walleye chop" category—as they'd say in the fishing vernacular-- when the crew left the dock. The big lake gets a whole lot rougher, but anyone venturing out in a 16-foot fishing boat on this morning would have been in for a bumpy ride.
Crews leaving the dock to check their nets once were a common sight in Warroad, which was a hub for commercial fishing activity on Minnesota's side of Lake of the Woods, but the last commercial fisherman out of Warroad pulled his nets for good in the 1980s.
These days, Lake of the Woods supports a thriving sportfishing industry, and the only nets to see water other than landing nets come from DNR fisheries crews. Every September beginning the Monday after Labor Day and continuing for about three weeks, a crew from the DNR's area fisheries office in Baudette, Minn., probes the depths of Lake of the Woods to get a handle on what's down there.
What's down there has a direct impact on the sportfishing industry. At the very least, it gives anglers an idea of what they can expect.
"It gives us an idea of what is down there right now—the important part of the fish population we want to catch and anglers want to harvest," said Tom Heinrich, large lake specialist for the DNR in Baudette.
According to Heinrich, the fall gillnetting survey has been a standard assessment on Lake of the Woods since 1968, with the exception of a few years in the 1970s when the survey was discontinued.
As part of the survey, the DNR sets four nets at each of 16 sites along the Minnesota's 300,000-plus-acre share of Lake of the Woods from the South Shore to the Northwest Angle. The crew sets the nets one day, leaves them overnight and returns the next morning to see what they hold.
The 250-foot nets have five, 50-foot panels of varying mesh sizes to capture fish of various sizes.
The goal of the survey is sample juvenile fish ranging from 10 inches up to about 25 inches, Heinrich said. The nets are set in the same locations every year.
"Bottom line is we have a long data series, which is nice," he said. "We can really see trends."
On this morning, the crew was checking nets set in about 7 feet to 20 feet of water in an area from Willow Creek near Rocky Point west to Swift Ditch. Brett Nelson, DNR fisheries specialist, manned the boat, while Heinrich and fisheries technician Zach Pawlowski pulled the nets, placing them into green tubs for the ride back to shore, where the fish would be removed and sorted.
Walleyes, saugers and perch, along with white suckers and tullibees, are the five most common species to show up in the nets, Heinrich said.
"Then just a whole slew of other things—everything from redhorse suckers to every now and then we see burbot, although they don't sample in the gillnets very well, so we don't see them very often," Heinrich said. "And now the last few years, we've seen a lot more whitefish and black crappies, too."
The whitefish surge, is interesting, Heinrich says, although he's at a loss to explain it.
"There are whitefish both upstream and downstream of us, so that could be a source, but when they took off, I don't know," he said.
The four nets produced a mix of walleyes ranging from 5- or 6-inch fish hatched this spring to specimens that would have put a smile on any angler's face. There also were saugers, perch, northern pike and an abundance of rough fish, including a quillback carpsucker that would have given the state record of 7 pounds, 4 ounces a run.
Pulling nets was the easy part, and despite the choppy waves, the crew completed the job in a couple of hours.
"These sites can be hit or miss, but we definitely hit them today," Heinrich said.
The grind begins
The slow, tedious work began back on shore, where Heinrich was joined by Dennis Topp, assistant DNR area fisheries supervisor in Baudette, to pick fish from the nets and sort them outside the public fish-cleaning house.
Inside, Nelson weighed and measured every fish of every species while Pawlowski entered the data into a tablet touchscreen computer.
A crew of Warroad-area volunteers filleted the game fish, which are donated to area senior citizen groups.
Nelson cut open the game fish before they hit the filleting table to determine their sex and stage of sexual maturity. He also removed otolith ear bones from a sample of the game fish. Cut into cross-sections, the otoliths under a microscope show rings that allow the biologists to age the fish, similar to the process for aging a tree.
"All of that (information) allows us to see whether we've got a strong year-class coming up and how quickly they're growing—what length at each age and at what age they are becoming sexually mature," Heinrich said. "If we see changes occurring in any of those metrics, that gives us an idea changes are taking place in our fish population, and then we have to address them."
Catch rates can vary considerably between sites and years, Heinrich said. Typically, he said, offshore sites, which have been part of the survey since 2002, produce larger walleyes and more saugers than the nets set closer to shore.
The long-term average for walleyes in the survey is about 15 to 17 fish per net, Heinrich said, but occasionally there are blips. That's what happened two years ago, when nets in the Northwest Angle yielded an average of 40 walleyes per net, and a single net set near Driftwood Point produced a whopping 135 walleyes.
That's always a productive site anyway, Heinrich said, but something—food, perhaps, or possibly water temperature—drew more walleyes than usual to the area.
Populations tend to cycle based on the strength of year-classes, the fish hatched during a particular spring. According to a Lake of the Woods report on the DNR website, the big lake has more large walleyes today than it did in the early 1980s, but the relative abundance of male walleyes has declined.
An increase in fishing pressure since the early 1990s could be a factor, the report said. And while the decline is concerning, there still are enough male walleyes on the spawning run to fertilize available eggs, the report said.
Heinrich, who's wrapping up his 26th fall gillnetting survey, says the survey results over the long term indicate Lake of the Woods' walleye population is healthy. And while anglers might not always agree with that assessment, the fish the crew brought back to shore in Warroad made a strong case.
"Our harvest is within a level we're comfortable at, and our fish population is doing fine," Heinrich said. "We have a lot of age classes out there, and nothing is missing. Our fish are getting old, so that suggests anglers aren't overharvesting them or anything.
"We routinely see fish up to like age 15 to 20 every year. Not a lot of other lakes have that."
• On the Web:
For more information on Lake of the Woods fisheries management, check out the DNR website at mndnr.gov/areas/fisheries/baudette/lowregs.html.