ST. PAUL — A group of Mille Lacs Lake residents sued the Minnesota Department of Natural Resources on Thursday, claiming the agency has mismanaged the lake’s struggling walleye population.

DNR officials didn’t consider a 1998 state constitutional amendment regarding Minnesota’s fishing and hunting heritage when developing its walleye management plan for the lake, attorney Erick Kaardal said. Instead, the agency focused only on a treaty with the Ojibwe bands that grants separate fishing rights, he said.

In doing so, “they’ve destroyed the Mille Lacs Lake walleye fishing heritage,” Kaardal said. “There’s no more important Minnesota ecosystem than the Mille Lacs Lake walleye fishery.”

DNR spokesman Chris Niskanen said agency officials couldn’t comment on the lawsuit because they hadn’t reviewed it thoroughly.

The DNR has imposed regulations to limit the walleye harvest this year, including a ban until December on night fishing, a lucrative line for resorts. Kardaal said the lawsuit seeks to restore night fishing and consider Minnesota’s fishing and hunting heritage when making any and all future rules.

The 1998 amendment included a passage that declares hunting and fishing “a valued part of our heritage that shall be forever preserved for the people and shall be managed by law and regulation for the public good.”

Residents say Ojibwe netting and spearing during spawning season is a major reason for the decline. They also cite DNR rules prohibiting anglers from keeping larger walleye, which they say leaves too many big fish to eat smaller fish.

“The DNR absolutely has not biologically managed this lake like it’s supposed to,” said Terry Thurmer, 60, a Garrison resident who owns Terry’s Boat Harbor.

“They are wrong on both counts,” Niskanen said.