The number of walleye in Lake Mille Lacs has dropped to the second-lowest levels since the state began monitoring fish populations in 1983, the state Department of Natural Resources said in a statement released Thursday.
DNR officials said the decline may have been prompted by a drop in the number of young walleye's primary food source — young perch.
That shortage of food could have resulted in a greater number of walleye that are small enough to be legally caught. State regulations require anglers to catch mostly smaller fish. Anglers are required to release all walleye between 20 and 28 inches long. Regulations allow each angler to keep just one walleye more than 28 inches long.
"Fisheries managers understand that a smaller perch population typically results in hungry walleyes, especially of the sizes anglers prefer to keep," the DNR statement said.
"Looking to 2012, a resulting high harvest would be a concern if it is projected to reach or exceed the state's allocation, which will be set in February in cooperation with Chippewa Band managers."
The department relies on netting assessments to estimate the number of walleye in the lake. This year's assessment found the lake's walleye index dropped from 10.8 fish per net in 2010 to 9.7. Measured in pounds, the index dropped from 22.9 pounds per net in 2010 to 16 pounds per net this year.
Although DNR officials said the assessment found "a smaller than anticipated walleye population," the department also noted that the male walleye population has been on a long-term decline since the mid-1980s.
"This may reflect the fact that the walleye harvest strategies employed by both the state and the Chippewa Bands are more selective for smaller, male walleyes," the statement said.
DNR officials said "good fishing may continue this winter and spring," despite the lower numbers.
"The implications of the decline in males to the overall fishery are not clear," the DNR statement said. "Fisheries biologists are evaluating the new data to better understand those implications and how they might influence future management options."
The assessment also found a decline in the number of northern pike in Lake Mille Lacs. DNR officials said that was expected, given a change in fishing regulations this year. The new regulations prohibit anglers from keeping northern pike 27 to 40 inches in length and allow anglers to take only one northern pike longer than 40 inches.
The old regulations protected northern pike from 24 to 36 inches and allowed anglers to take only one northern pike longer than 36 inches.