In an unprecedented move, late-night fishing on Lake Mille Lacs, a sport unto itself for generations of Minnesotans, has been banned for the coming fishing season, except for opening weekend.

The annual spring night fishing ban on the state's premier walleye fishery will be extended until December, rather than ending in mid-June, in an attempt to help the lake's struggling walleye population recover, the Department of Natural Resources announced Tuesday.

The DNR wants to avoid the alternative: Restricting walleye fishing to catch-and-release only for the season, an option that local businesses and anglers would find tough to swallow.

Mille Lacs will be off limits to all anglers from 10 p.m. to 6 a.m. beginning May 12, the Monday after the fishing opener. The change will affect not only individual anglers but resorts that operate large launches to take groups onto the lake to fish at night, when walleyes tend to bite more often.

"The launch businesses probably will take a 70 percent hit," said Terry Thurmer, owner of Terry's Boat Harbor on Mille Lacs, which operates two launches. "It hurts. Last year business was down, and now it will be down even more.''

The walleye harvest must be reduced because the population is at a 40-year low. The DNR and eight Chippewa bands that manage the lake agreed earlier this winter to a safe walleye harvest of just 60,000 pounds — the lowest ever and less than a quarter of the 250,000 pounds allowed last year. This year's quota is a 90 percent drop from the 600,000 pounds allowed less than 10 years ago.

Of the 60,000 pounds, 42,900 pounds is allocated to the state and 17,100 pounds goes to the bands.

Don Pereira, DNR fisheries chief, said Tuesday that without the night ban, the DNR might have to end walleye harvest altogether this season and make it a catch-and-release-only fishing. The night ban reduces that possibility, but doesn't eliminate it.

"It was a very difficult decision,'' he said. "We know folks who run launch operations that will be affected. But we feel it's in the best interest of all users to avoid a catch-and-release fishery.''

The ban includes muskie anglers, many of whom fish at night. But allowing some anglers on the lake at night and not others would be problematic for enforcement, Pereira said.

"We're asking muskie anglers to make a sacrifice for us,'' he said.

The walleye possession limit will remain unchanged at two, and only walleyes 18 to 20 inches, including one longer than 28 inches, may be kept — the same regulation as last year. But relatively few fish that size are in the lake.

To try to balance the potential loss of walleye anglers to local businesses, Pereira announced the DNR will relax regulations on Mille Lacs for northerns and smallmouth bass. The northern limit will be increased to 10 — seven more than last year — with only one longer than 30 inches allowed.

And the northern season will be extended; instead of closing in mid-February, it will close the last Sunday in March. The northern spearing ban also will be removed.

Smallmouth bass fishing, meanwhile, will start with the walleye opener May 10 — two weeks earlier than normal — and will be exempted from the statewide catch-and-release regulation that begins in mid-September, meaning anglers can keep smallmouth from the opener until the last Sunday in February. The limit is six, with one over 18 inches allowed. Last year, anglers could keep six fish 17 to 20 inches, with one over 20 inches.

"I think it's a great idea,'' said Dean Hanson, owner of Agate Bay Resort. But he said he's not sure if anglers, long hooked on walleyes, will switch to bass or northerns. "They are delicious. We have to get them to try them.''

Pereira said bass anglers might not be happy with the liberalization of the regulations. "But the rate of production of small fish is high enough that we feel we can allow some harvest of smallmouth bass and still preserve the trophy quality of that fishery,'' he said.

George Liddle, who owns a cabin on Mille Lacs and started a petition last year to oppose the relaxation of bass fishing regulations, was aghast.

"It's absolutely going the opposite way of having a trophy smallmouth bass fishery, something coveted by so many places,'' he said.

Pereira said officials are investigating the causes of the walleye decline. Meanwhile, northern pike and smallmouth bass in recent years have been increasing dramatically. Young walleyes are not surviving well in the lake, and the DNR plans a detailed diet study to see what predators might be responsible.

"It doesn't appear smallmouth bass are problematic, but it appears northern pike could be,'' Pereira said.