Anglers fishing Upper Red Lake will have to keep the carcasses of walleyes and northerns they eat on the lake to prove the fish were legal size, beginning Jan. 12.

The change is in response to a state law passed last year by the Legislature allowing anglers fishing on waters with size restrictions, such as Upper Red Lake and Lake Mille Lacs, to cook a meal of the restricted fish while on the ice.

Previously anglers couldn't do that because they had to leave fish whole so they could be measured.

On Upper Red Lake, walleyes 17 to 26 inches -- the protected slot -- must be released, as do northerns 26 to 40 inches.

The law allowing fish to be eaten on the lake makes enforcement difficult because conservation officers can't determine if the fish being cleaned and consumed are of legal size, said Gary Barnard, Department of Natural Resources area fisheries manager in Bemidji.

"Our officers were looking for some accountability for the fish being eaten on ice to comply with the size regulations," he said. He said there are no indications that anglers are abusing the law, though some fear that is happening.

Many permanent ice fishing houses offer cooking and sleeping facilities.

The law says fish with size restrictions must be whole and measurable when in possession, except when on the ice and a person is in the act of preparing and using the fish for a meal.

The carcass requirement is only for Upper Red Lake, because the DNR was able to insert that language in new rules that were being established for the lake, Barnard said.

(Those rules call for a three-fish walleye limit next spring. The current daily and possession limit is two fish.) Cooked and eaten fish count toward the daily limit, officials emphasize.

That means anglers can take no more than two walleye per day and have no more than two in possession at any time.

The new carcass rule also might cause confusion, Barnard acknowledged. "If you're required to retain carcasses the day you consumed those fish, what do you do the following day? They can harvest fish the next day, but they need to get rid of those carcasses because they are considered part of your possession limit."

And Barnard said anglers are urged to dispose of the carcasses in the garbage, and not down their ice fishing holes.

"There are still plenty of ways to abuse the law, if they want to," he said. "But this provides a way for anglers to consume fish legally and provide accountability."

Anglers on Upper Red Lake must retain carcasses with head, spinal column and tail intact when cleaning a fish for a meal. Carcasses must be kept so they can be separated, counted and measured for the remainder of the day in which the fish were consumed.

Here are tips from the DNR for possessing walleyes or northerns on Upper Red Lake:

• Don't allow whole fish or carcasses to freeze together in buckets or bags, because they need to be measurable.

• Pack whole fish or carcasses in snow or ice shavings in a bucket or cooler inside the fish house to prevent freezing.

• Carcasses count toward a person's possession limit.

• It is illegal to dispose of fish carcasses on or under the ice.