About 40 people now face federal, state or tribal charges for buying and selling tens of thousands of walleyes netted from some of the state’s most popular walleye lakes, officials said Monday in announcing additional charges.

Officials said 21 northern Minnesota suspects will face state charges. That’s in addition to the federal felony charges against 10 people that were announced last week by the U.S. attorney’s office in Minneapolis. And up to 15 members of the Leech Lake Band of Ojibwe also face tribal charges.

It’s the largest such poaching case in 20 years.

“This is a very serious problem,’’ Tom Landwehr, Department of Natural Resources commissioner, said at a St. Paul news conference. And he said the problem isn’t just with Indian band members illegally selling fish they harvest.

“It’s just as illegal to purchase game fish as it is to sell them,’’ he said. “Without buyers there wouldn’t be sellers.’’

The walleyes came from some of Minnesota’s most storied fishing lakes, including Leech, Winnibigoshish, Cass and Red.

Jim Konrad, the DNR’ s chief enforcement officer, explained the work of investigators in Operation Squarehook.

The allegations culminate a three-year investigation called Operation Squarehook, involving 60 DNR and U.S. Fish and Wildlife Service officers and tribal authorities from the Red Lake Band of Chippewa and Leech Lake Band of Ojibwe. Squarehook is slang for a fishing net, which has many squares to ensnare the gills of fish.

Widespread acceptance of the illegal buying and selling of game fish must change if the long-standing northern Minnesota practice is to be curtailed, state officials said.

“It’s an accepted cultural norm up there that people buy and sell fish,’’ said Jim Konrad, the DNR’s chief enforcement officer. “We hope to change this culture. [But] until people stop buying illegal fish, the suppliers will continue to catch and sell them.’’

Officials doubt the case will end such fish poaching.

“Certainly we didn’t catch everybody who was buying and selling fish,’’ Konrad said. “We believe there is a lot more of this activity going on out there.”

Officials said the poaching, while widespread, was loosely organized. “It was very informal and word-of mouth rather than anything organized,’’ Konrad said.

He said DNR officers will continue to pursue poaching tips they receive.

A history of fishing problems

There’s a long history of such activity. In 1993, 45 people were charged with criminal conspiracy to illegally transport, take, sell and buy walleyes from the Red Lake and Leech Lake reservations. And the collapse of the Red Lake walleye fishery in the 1990s was blamed on overfishing, some of it illegal. It has since been restored.

In the latest case, the poaching of so many fish took harvest opportunities away from sport anglers and band members, but it’s impossible to know whether fish populations on affected lakes were hurt, said Henry Drewes, DNR regional fisheries manager in Bemidji.

“There’ll be no changes to the [sport fishing] bag limits,’’ Drewes said.

Among those charged last week in federal indictments were a restaurant owner and a tavern owner, but officials said Monday that all of the fish bought illegally were for personal use or were sold again.

“As far as we know, they [fish] were coming in the backdoor, and going out the backdoor,’’ Konrad said.

Walleyes were the primary target of buyers and sellers. During the investigation, officers found sites where large amounts of other, non-target fish, including northern pike, were dumped.

“Those fish were just wasted,’’ said Konrad. Officials released photos from two of the sites, including one where the walleyes had been fileted and the entrails left behind in a pile.

Charges in tribal court, too

Jamie Mitchell, chief conservation officer of the Leech Lake Band, said the band’s conservation code prohibits the commercialization of game fish.

“We do not condone the sale of game fish,” he said. He said 10 to 15 band members are expected to face charges in tribal court and the possibility of fines and the loss of hunting and fishing privileges.

The Red Lake Band allows subsistence angling for walleye; the Leech Lake Band allows for subsistence angling or netting for walleye. But band members can’t sell the fish. The Red Lake Band has a legal commercial walleye fishery, but band members can only sell their fish to the tribe-operated processor.

The fish were sold for $1.50 to $3 per pound, far less than the $10 to $17 per pound for legal walleyes sold in grocery stores.

Six counties involved

The DNR said the 21 suspects in the state case face up to 35 misdemeanor and six gross misdemeanor charges in six northern Minnesota counties — Clearwater, Polk, Itasca, Cass, Pennington and Beltrami. The illegal sale and purchase of game fish is a misdemeanor or gross misdemeanor, depending upon the value of the fish involved.

The misdemeanors are punishable by a maximum fine of $500 and/or up to 90 days in jail. The gross misdemeanors, involving the sale of more than $50 of game fish, could result in a maximum fine of $3,000 and/or up to a year in jail. The federal charges brought last week are felonies because they allege violations of the Lacey Act and carry stiffer penalties.

At least two people have already pleaded guilty and paid fines, Konrad said.

“This is a troubling case because it involved large numbers of people and a significant number of fish being illegally bought and sold,” said Landwehr. “The investigation should serve notice that the illegal commercialization of walleye and waste of game fish will not be tolerated in Minnesota.”