Aged Trout Shows Value of Fish Refuges

DNR fisheries biologist Brad Ray displays a lake trout hatched nearly 50 years ago. It was captured and released earlier this month during a DNR lake trout assessment on Lake Superior. Photo by David Stokes/Stokes Media House Inc.

State fish biologists conducting spawning surveys on Lake Superior hauled in a lake trout earlier this month that hatched when Richard Nixon was president.

The fish was originally caught and released during Wisconsin Department of Natural Resources’ spawning assessments for lake trout in 1981. It was caught and released again Nov. 2 in the same fish refuge, the Gull Island Shoal of Lake Superior.

“We often think of a fish’s lifespan being relatively short, maybe 10 years,” said Terry Margenau, DNR fisheries supervisor. “But lake trout are slow growing and have a longevity that will rival that of the ancient sturgeon. This fish is a prime example of that longevity and the important role fish refuges play in sustaining populations of these native fish.”

No fishing of any type is allowed in two fish refuges in Wisconsin waters of Lake Superior. The Gull Island Refuge was established in 1976 and the Devils Island Refuge in 1981. “Creating these protected areas was the primary driver of the recovery of lake trout following their depletion from sea lamprey invasion and overharvest,” said Brad Ray, senior fisheries biologist for DNR in Bayfield.

To help assess the condition of lake trout on Lake Superior, DNR has been conducting spawning lake trout assessments since 1951. Part of the assessment includes tagging the fish caught and releasing them so biologists can monitor their growth and movement in future years.

The fish caught Nov. 2 had first been tagged in 1981 when it was 27.3 inches during a DNR spawning assessment on Gull Island Shoal of Lake Superior. The same fish was handled again in 2017 during the same spawning assessment and measured 35.5 inches, Ray said.

“This lake trout grew about eight inches in 36 years, or less than a quarter inch per year,” he said. “So very slow growing. Its age is also interesting. Considering this fish was likely 10-12 years old when it was tagged in 1981, this fall it would have been at least 46 years old.”

Doing the math, the lake trout hatched from an egg in the early 1970s, when Richard Nixon was president, the Vietnam War was ongoing, and John Lennon wrote his hit song “Imagine.”

The same fish would be caught by DNR seven more times during surveys, Ray says.

In all of those instances, the fish was captured in the Gull Island Refuge.

“The spawning site fidelity of this fish, and many others we have sampled, emphasizes the importance of the refuges and the protection it affords the spawning stock of lake trout,” he said.

Anglers fishing Lake Superior will want to keep an eye out for the next geriatric fish, a survivor and a foundation for the fishery. All lake trout DNR fish crews handle receive a numbered colored tag. Anglers who catch a tagged lake trout and intend to release the fish, should just write down the tag number and contact the Bayfield DNR office to get the capture history.