A team of US researchers has determined the age of the oldest known lake trout ever recorded in the Great Lakes. That fish, dubbed grandma Mary Catherine, was 62-years old — making it a full 20 years older than the former record.
The fish was collected in fall 2023 from Lake Superior by a team of researchers from the Michigan Department of Natural Resources, the US Fish and Wildlife Service, the University of Wisconsin-Milwaukee, and Purdue University. They were conducting a special survey to investigate different forms of lake trout over Klondike Reef.
Using the fishʼs otoliths (ear bones) researchers determined that Mary Catherine hatched in 1961. As a humper, a smaller and less abundant form of lake trout, it weighed only 4.62 pounds and measured 25 inches — far smaller than you might expect for a fish of her age. The discovery speaks to the extraordinary and uncommon success of Lake Superior’s lake trout recovery, Ontario Federation of Anglers and Hunters Fisheries Biologist Adam Weir said.
“By the mid-1900s, Great Lakes lake trout were on the brink of extirpation due to overfishing and predation by sea lamprey, but now, they are considered fully recovered in Lake Superior due to the binational efforts of various agencies and stakeholders. This fish is a symbol of what can be achieved by these conservation efforts,” he added.
Originally published in the Fall 2025 issue of Ontario Out Of Doors
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