Walleye fishing has been hot on Lake of the Woods in recent months.

Maybe too hot.

Last week, 40 state conservation officers descended on the lake — one of Minnesota's most popular — and executed search warrants as part of a fish poaching investigation that began last summer and involve numerous violations.

About two dozen people, including some fishing guides, are expected to be cited. Many of the cases appear to involve "double-tripping" where anglers catch fish, leave the lake, then return and catch more than their limit.

"They'd take a limit of fish, come in, eat those fish or store them, then go back out and take more fish that day,'' said Col. Ken Soring, Department of Natural Resources enforcement chief. Others will be cited for violation of the protected slot. Walleyes 19½ through 28 inches must be released on Lake of the Woods. The possession limit is four walleyes.

Minnesota's fish possession limit is just that: The total number of fish an angler can have in possession, whether in the freezer or on a stringer. And fish that are caught and eaten must be counted as part of a person's possession limit the day of the catch.

"If the limit is six fish, and you go out an catch your six fish and eat them, you can't go out and keep more that day,'' Soring said.

News about the case spread fast, even though the DNR hasn't publicized it.

"Everyone is aware of it,'' said Paul Arnesen of Arnesen's Rocky Point Resort. "I don't know anything about what took place. My hope is everyone would follow the regulations. We strive to do that.''

How widespread was the poaching?

"We believe it was happening with quite a bit of frequency,'' Soring said.

And some guides and businesses allegedly were complicit.

"While the investigation showed that many operations were doing the right thing and encouraging their guests to comply with regulations, some were violating the laws and encouraging others to do the same,'' Soring said. "Those are the ones we'll be charging.''

The investigation started last summer, he said. Soring wouldn't discuss details of the investigation or say whether officers worked undercover. But he said documenting such illegal activity can be difficult for uniformed officers.

"Some people will be opportunistic when the fish are really biting,'' he said. "But you can have a great day catching and releasing fish. We have some of the best fishing in the nation. You can catch enough fish to eat, but you need to not take too many so our kids and grandkids can have this same opportunity.''

Conservation officers are completing reports and compiling evidence in preparation for charges, which are expected to be filed in the next week or two, Soring said. All most likely will be misdemeanors, he said.

Lake of the Woods receives more total fishing pressure than almost any other lake in the state, said Henry Drewes, DNR regional fisheries manager in Bemidji. Fishing on Lake of the Woods was excellent in December and very good last summer, too, Drewes said.

"The Lake of the Woods walleye and sauger fisheries are in excellent shape, and enforcing regulations is a part of taking care of those fisheries.''

Doug Smith • 612-673-7667