For years, Mille Lacs walleye anglers have been governed by harvest quotas, catch-and-release restrictions and night fishing bans — all of which will be in place again this season.

Now for the first time, the 132,000-acre lake will go dark for walleye fishing during the heart of summer.

The July 7-to-July 27 walleye fishing hiatus was announced Tuesday by the Department of Natural Resources (DNR) to keep anglers from prematurely exceeding a summer quota that at 29,000 pounds is the lake's lowest ever. Without the closure, the DNR fears that thousands of walleye caught by Mille Lacs anglers and freed into midsummer's warm lake water would die by so-called hooking mortality. Last year, a spike in hooking mortality during the last two weeks of July accounted for more than half of the state's walleye allocation.

"The closure [will] coincide with the hottest part of the summer, when released fish are vulnerable to stress," DNR fisheries chief Don Pereira said. "Warm water combined with July's higher fishing pressure means that more fish die — even those that are caught and returned to the water."

The DNR has comanaged Mille Lacs fisheries with eight Chippewa bands after the bands' off-reservation hunting and fishing rights were affirmed by the U.S. Supreme Court in 1999.

This year's restrictions — including a season-long catch-and-release rule — are necessary for multiple reasons, Pereira said, including:

• Anglers caught more and bigger walleyes this winter on Mille Lacs than expected — some 14,000 pounds. These fish count against the state's 2017 Mille Lacs 44,800-pound walleye allocation.

• Anglers exceeded their Mille Lacs walleye harvest quota last summer and must "pay back" 6,800 pounds of walleyes, prorated over four years, or 1,700 pounds annually, beginning this year.

The problem with Mille Lacs walleyes, Pereira said, is a decline in overall population and historically low rates of baby fish living to adulthood. The 2013 year class is very strong, and those fish, now about 14 to 16 inches long, represent hope the lake's walleye breeding stock will be replenished in coming years.

"We know 2014 walleyes are in very low abundance," Pereira said. "And it's a bit early to see how the 2015 and 2016 fish are doing."

The DNR is unsure just why Mille Lacs walleyes are disappearing as they age, though predation by older walleyes and other larger fish is thought to be part of the problem.

A possible contributing factor is that yellow perch and tullibees, which traditionally have provided forage for Mille Lacs walleyes, are in relatively short supply. "Why" is unknown. Perhaps these fish, along with small walleyes, are being eaten by larger fish. Or maybe their disappearance is a byproduct of other issues at Mille Lacs, such as a breakdown in the lake's food chain due to an explosion of zebra mussels and a second invasive species, spiny water flea.

DNR biologists and their tribal counterparts met in recent weeks to develop a 2017 Mille Lacs walleye "safe harvest level." The meetings reportedly were argumentative at times because the Chippewa were upset that Gov. Mark Dayton allowed state walleye anglers to continue fishing last summer after their quota was met.

Ultimately, the DNR and the bands agreed to a 64,000-pound safe harvest level, with the state getting 70 percent, or 44,800 pounds, and the Chippewa 30 percent.

The bands also agreed that state anglers can add an additional 11,000 pounds to their quota, for a total of 55,800 pounds, if necessary to keep the walleye fishing season open until Sept. 4.

Such overages must be repaid out of future allotments, however. "We don't want to [take the additional fish], because paying back the overage will reduce our take in future years," Pereira said.

Resort owner Terry McQuoid disagrees with the DNR about the number of walleyes in Mille Lacs.

"Their data about how many walleyes are in the lake is skewed," McQuoid said. "You can't catch as many walleyes as we did this winter and last summer and have a lake in crisis. This winter we had some rental houses that caught 25 to 40 walleyes a weekend, of all sizes. That's never happened."

Opening day for walleye fishing statewide is May 13, and walleye angling on Mille Lacs closes for the year on Labor Day.

Dennis Anderson contributed to this story