The effort to save the Lake Mille Lacs tourism industry in the face of an abrupt halt of the cherished walleye fishing season Monday will be ecologically, economically and legally complicated.

That’s what legislators and others on a new working group heard repeatedly Tuesday at their first meeting.

Legislators remained incredulous that a special legislative session is actually needed or that the Department of Natural Resources (DNR) is not able simply to extend the walleye season through Labor Day despite the population collapse.

Donald Pereira, a DNR biologist, laid out a complex problem he said was caused by various factors, including too many fish dying when they were released, invasive species, prolific predator fish and climate change.

Spiny waterfleas, native to Europe and Asia, eat zooplankton, which is supposed to be food for native fish.

The Clean Water Act has improved lake clarity, but that has sent younger walleye into deeper parts of the lake, where they are often prey for predators, including older walleye.

Warmer water temperatures increase hook mortality, or the rate at which fish die after being caught and released.

If some prevailing climate change models are correct, resulting warmer temperatures would be fatal in the long-term for tullibee (or cisco), which is important walleye prey, Pereira said.

Stocking the lake would be more complicated than the successful stocking at Red Lake, where there was no walleye fishing for seven years.

In the short term, both Sen. David Tomassoni, DFL-Chisholm, co-chairman of the working group, and Sen. Rod Skoe, DFL-Clearbrook, questioned why DNR did not continue the season regardless, at least through Labor Day.

“I’m just shocked, commissioner,” Tomassoni said.

DNR Commissioner Tom Landwehr said extending the season would worsen the problem in future years and run afoul of the treaty agreement with the bands in the region, the largest of which is the Mille Lacs Band of Ojibwe.

Legislators also were skeptical that a special legislative session is required to help the tourism-related businesses there. Commissioner Katie Clark Sieben of the Department of Employment and Economic Development and Commissioner Myron Frans of Minnesota Management and Budget said the administration has no legal authority to spend what they estimated could be $10 million to $20 million on loans, tax abatements and advertising for the region.

Skoe, an influential chairman of the Senate Taxes Committee, said businesses do not want more debt and that debt forgiveness should be expected.

The working group will meet again Tuesday; administration officials will provide more detailed proposals.