MINNEAPOLIS (AP) — A new study is using underwater listening devices to find out why more young walleye in a Minnesota lake aren't making it to adulthood.
Acoustic telemetry will be used to track the movements of the juvenile fish in Lake Mille Lacs, Minnesota Public Radio News reported. The Mille Lacs Band of Ojibwe hopes to test a hypothesis that warming lake temperatures are contributing to the recent walleye population decline.
The band has partnered with the Great Lakes Indian Fish and Wildlife Commission and the Fond du Lac Band of Ojibwe for the study. The tribe received a grant of nearly $200,000 from the U.S. Fish and Wildlife Service for the study, which will run through the spring of 2019.
Scientists have placed 61 acoustic receivers in the lake in a grid pattern more than 9,800 feet (3,000 meters) apart. They aim to implant transmitters in about 70 adult walleye this month. Researchers will also tag 35 juvenile fish in the fall and another 35 this spring, said biologist Carl Klimah.
"We'll know roughly where that fish is, we'll know what depth it's at, we'll know what temperature it's occupying," Klimah said. "So there's a lot of information that comes with it."
Researchers hope to see if walleye are moving into smaller areas of the lake as they seek the optimal water temperature of around 68 degrees (20 Celsius). That movement could bring juvenile and adult walleye closer together and could increase the chances of the adult fish eating the younger fish, Klimah said.
Walleye fishing in Mille Lacs Lake has been limited to catch-and-release this summer. Minnesota Department of Natural Resources officials have said the walleye population shows signs of improving health, but angling restrictions are needed to help its recovery.