Perplexed by a complicated and underachieving Lake Mille Lacs fishery, the Department of Natural Resources said Tuesday that anglers can keep only two walleyes from the big lake when the state’s open water fishing season begins May 11.

And Mille Lacs walleyes that end up in a live well or on a stringer must measure between 18 and 20 inches — though one trophy larger than 28 inches can be kept.

The limit is half what it was a year ago, when anglers on Mille Lacs — arguably the state’s premier fishing lake — could keep four walleyes under 17 inches, with one over 28 inches.

“It’s going to hurt business,” said Terry Thurmer of Terry’s Boat Harbor and Marina on Mille Lacs. “Anytime we’ve had a 2-inch shot in the past, business dropped dramatically. People just go elsewhere.”

The cutback is needed, the DNR said, because Mille Lacs walleyes are at a 40-year low.

Reproduction in the lake in recent years has been good, officials said, but too few of the fish are surviving. Consequently, conserving the lake’s large 2008 walleye year-class — now 15 to 17 inches long — is important, because no strong year-classes follow it.

Without the new restrictions, anglers could exceed their “safe harvest quota” of Mille Lacs walleyes, which this year is 178,500 pounds — half the amount in 2012.

A quick rebound of the lake’s walleyes is unlikely, DNR fisheries chief Dirk Peterson said.

“I think we’re looking at least a two- to three-year period” that tighter harvest restrictions will govern the lake, he said.

Mille Lacs walleyes also are netted by eight Minnesota and Wisconsin Chippewa bands whose quota similarly was cut in half this year, to 71,250 pounds.

The bands again will net Mille Lacs during the spring spawn. But they’re being encouraged “to balance [their harvest method]” in an attempt to make their take more “small-fish friendly,” said Charlie Rasmussen of the Great Lakes Indian Fish and Wildlife Commission, which represents 11 Chippewa bands in Minnesota, Wisconsin and Michigan.

“We’re encouraging tribal harvesters to do more spearing,” Rasmussen said, “to expand the size of the fish that are harvested.”

Among non-band members around the lake, Chippewa nets are widely blamed for the Mille Lacs walleye decline, a position also espoused by a new group called Save Mille Lacs Sportfishing (savemillelacssport

The group issued a statement late Tuesday saying it hoped to take the DNR to court and force an end to Chippewa netting.

But the DNR believes other factors might play roles, including the lake’s larger northern pike and smallmouth bass populations, warming water temperatures brought on by climate change, the relatively recent arrival of invasive species such as zebra mussels, and possibly the agency’s own Mille Lacs-specific harvest regulations.

Liberal on smallmouth

The DNR also announced Tuesday that Mille Lacs smallmouth bass and northern pike regulations will be liberalized this season, in part as a way to entice anglers to keep coming to the lake.

Last year, the smallmouth bass limit was one over 21 inches. Beginning with the bass opener in late May, the limit will be six, with a protected slot of 17 to 20 inches (only one smallmouth bass can exceed 20 inches).

Similarly, a larger Mille Lacs northern pike harvest will be encouraged by a new 33- to 40-inch protected slot (with one fish allowed over 40 inches in a three-fish limit) — a big change from the 27- to 40-inch protected slot that regulated northern pike takings on the lake a year ago.

Thurmer believes the changes will do little to mitigate the effect on resort and bait shop owners, among other Mille Lacs area businesses.

“The reputation and tourism that Mille Lacs has had all of these years is because of walleyes, not northerns and smallmouth bass,” he said. “It will in no way replace the business we lose.”

Implicit in the new Mille Lacs walleye regulations are harvest projections the DNR developed based on past years’ angling pressure and catch rates.

If the coming year proves to be an outlier to those estimates — if the walleye bite is either faster or slower than projected, for example — the DNR might have to alter its regulations, making them more liberal or still more restrictive.

A worst-case scenario, for example, would unfold if a hot walleye bite this summer puts too many 18-20-inch walleyes in anglers’ boats, forcing the DNR to implement more restrictions to avoid exceeding the safe-harvest quota.

But even that move would be problematic, because the DNR includes an estimated 100,000 pounds of “post-release mortality” in the 178,500-pound sport-fishing quota.

Meaning even a total catch-and-release walleye fishery would result in a continued “harvest.”

Still, Suzy Fisher of Fisher’s Resort near Isle remains hopeful.

“The bite is expected to be very good this year,” she said. “I’ve only had a few people say they’re not coming because of the regulations.’’