Fisheries biologists have uncovered a remarkable fish story in Lake Superior: Mary Catherine, a lake trout (Salvelinus namaycush), is now believed to be the oldest lake trout ever recorded in the Great Lakes. Hatch year: 1961. Caught during a routine survey in September 2023 on Klondike Reef, a remote reef in Lake Superior, Mary Catherine was found to be 62 years old, twice the age expected for a lake trout under ordinary conditions.
In September 2023, fisheries crews working Klondike Reef in Lake Superior aged a lake trout, affectionately nicknamed “Mary Catherine”, at 62 years old, making her the oldest lake trout documented in the Great Lakes. She’s a humper-form lake trout, small-bodied but long-lived, and biologists confirmed her age by reading growth rings on otoliths (ear stones), the gold standard for old fish. Reports note she was hatched in 1961, which means this single trout lived through sea-lamprey decimation, fishery closures, and multi-decade restoration—then outlived most of her species several times over.
That longevity arrives alongside a broader rebound story: in Minnesota’s portion of Lake Superior, 98% of lake trout sampled in 2023 were wild, a striking indicator of self-sustaining populations after decades of lamprey control, habitat protection, and careful harvest management. Source: Minnesota DNR Files (PDF)
A Life Lived Across Keweenaw History
If Mary Catherine truly hatched in 1961, she “saw” plenty: C&H Mining still operating; a ~95% Great Lakes lake-trout collapse by 1964 from overfishing and lamprey; the 1986 EPA Superfund designations at Torch Lake and Quincy Smelter; the 1992 creation of Keweenaw National Historical Park; and the present-day recovery of native fish communities in Superior’s cold, clear water.
Counting Rings & Setting Records
Usually, lake trout in Lake Superior live around 25–30 years. The previous oldest known trout in Superior was about 42 years old, recorded in 1998. Mary Catherine weighs about 4.62 pounds (2.1 kilograms) and measures just under 25 inches (627 mm) long. A modest size, but astounding longevity.
She is of the “humper” subspecies, which are known for relatively slow growth and feeding predominantly on invertebrates—traits that may contribute to longer lives. Biologists estimated her age by counting growth rings on her otoliths (inner ear stones), where one ring forms each winter.
What’s at Stake: Why This Matters
That Mary Catherine survived through decades of environmental stress, threats from overfishing and sea lamprey, changing water quality, and variable climate implies something positive: the lake trout population in Lake Superior is in relatively strong shape. Her longevity is more than trivia, it’s a signal.
In fact, in 2024 state, provincial, tribal, and federal agencies declared that lake trout populations in Lake Superior are now “fully restored.”
Looking Back: Mary Catherine’s Lifetime in Context
Since 1961, when Mary Catherine hatched, a lot has happened locally around Lake Superior. Here are some selecting landmarks that span her life:
- 1961: C&H Mining Company (Calumet & Hecla) was still in operation.
- 1964: Lake trout populations across the Great Lakes dropped nearly 95% due to overfishing and invasive sea lamprey.
- 1986: The U.S. Environmental Protection Agency (EPA) identified sites along Torch Lake and the Quincy Smelter as potential Superfund cleanup locations.
- 1992: The Keweenaw National Historical Park was established.
- 2024: Lake Superior’s lake trout population declared fully restored.
It’s rare that a single living fish has been a silent witness to so much regional history, including environmental battles, mining era legacies, conservation reforms, and evolving community relationships with the lake.
Second Oldest Fish & Other Notables
While Mary Catherine now holds the top spot among recorded ages for lake trout in the Great Lakes, there have been other impressive specimens and related stories:
- The previous record for lake trout in Lake Superior was a 42-year-old fish, caught in 1998.
- Another example (not lake trout) is the “bigmouth buffalo” species, found elsewhere in North America, known to live for over 100 years, setting records among long‐lived freshwater fish. Source: Wikipedia
These stories reinforce how long‐lived many native fish can be, under the right conditions of cold, clean water, limited pollution, and good habitat.
How Old Do Lake Superior’s Native Fish Get?
Mary Catherine’s 62 years is extraordinary—but she’s not the only elder in Superior’s neighborhood. Here’s how she compares with other native species (and native coregonines closely tied to Superior’s food web). “Max ages” reflect the oldest documented in credible studies or agency synopses; “typical” gives a realist’s range anglers and biologists often observe.
| Species (native) | Oldest documented / typical | Notes & sources |
|---|---|---|
| Lake trout (Salvelinus namaycush) | 62 years (Mary Catherine, 1961–2023); typical 25–30 years | Otolith aging on a humper-form trout from Klondike Reef; previous Superior record ~42 yrs (1998). GovDelivery (Doc) |
| Lake sturgeon (Acipenser fulvescens) | Up to ~154 years; typical M ~50 / F ~75 | Longest-lived native Great Lakes fish; very late-maturing. Shedd Aquarium |
| Lake whitefish (Coregonus clupeaformis) | Up to ~50 years; typical ≤25 years | Cold-water coregonine; some very old fish recorded in literature. |
| Cisco / lake herring (Coregonus artedi) | 20+ years | GLFC and USFWS materials recognize cisco as long-lived with sporadic strong year-classes. Great Lakes Fishery Commission (PDF) |
| Kiyi (Coregonus kiyi) | ♀ to 20 years (otolith-based) | Recent USGS/TAFS work shows females reaching ~20 yrs in Lake Superior. U.S. Geological Survey Publications (PDF) |
| Bloater (Coregonus hoyi) | Up to ~11 years (documented) | Some accounts once underestimated coregonine ages using scales; otoliths improved precision. Department of Environmental Conservation (PDF) |
| Burbot (Lota lota) | Up to ~20 years; often ≤10–12 | Superior studies highlight long life and resilience of this native cod-relative. |
| Northern pike (Esox lucius) | >20 years (occasionally) | MN DNR notes pike can exceed 20 years, though many live far less. Minnesota DNR (PDF) |
| Muskellunge (Esox masquinongy) | ~30+ years | Agency syntheses cite individuals to 30+ years. U.S. Fish and Wildlife Service (PDF) |
| Brook trout (incl. coaster form) (Salvelinus fontinalis) | Typically <10 years in Superior; coaster captures commonly ≤6 yrs | MN DNR coaster work in Superior shows age-1 to age-6 most common. Minnesota DNR Files (PDF) |
| Deepwater sculpin (Myoxocephalus thompsonii) | Up to ~7 years (Superior) | Selgeby’s classic work placed Superior max age at ~7. Sara Registry (PDF) |
Why the spread? Cold, stable, low-productivity waters—like Superior’s offshore—tend to favor slower growth and longer life. Better age methods (sectioned otoliths) have also pushed known maxima upward for several species over the last two decades. Source: Great Lakes Fishery Commission (Downloadable Document)
Why Mary Catherine Matters
Finding a 62-year-old trout in 2023 is a testament to the lake. Decades of lamprey control and careful harvest brought Superior’s native predators back to a largely self-sustaining state, with survey crews now reporting very high proportions of wild trout in Minnesota waters (98% in 2023). That resilience echoes across the food web—the same USGS and GLFC surveys that track lake trout also show big, episodic cisco year-classes that can shape the next decade of forage. Source: Minnesota DNR Files (Downloadable Document)
Want to Go Deeper?
- MI DNR “Showcasing the DNR” write-up (text version): background on the 62-year trout. GovDelivery (Downloadable Document)
- USGS + Lake Superior Technical Committee resources on otolith aging (and why it matters for old fish). Great Lakes Fishery Commission (Downloadable Document)
- GLFC/USGS annual Lake Superior fish community reports: recruitment pulses and long-term trends. Great Lakes Fishery Commission (Downloadable Document)
- Shedd Aquarium’s lake sturgeon synopsis for the truly ancient of the Great Lakes.
Your Turn!
What’s the biggest historical shift that’s happened in your lifetime along the South Shore? Drop it in the comments! We’ll add the best ones to a reader timeline right alongside Mary Catherine’s 62-year journey.
