Don't call the bigmouth buffalo a "rough fish," a common and derisive moniker slapped on species viewed as less desirable than the sainted walleye and other hotly pursued fish.

"They are amazing," said Alec Lackmann, a North Dakota State University researcher in the Department of Biological Sciences. "They are one of the most exceptional freshwater fish species in the world."

Lackmann would know. He led an NDSU team that unearthed this amazing fact: Bigmouth buffalo can live to be more than 100 years old, making them the oldest age-validated freshwater fish in the world.

Lackmann's study included one specimen that was 112 years old, and most of the fish he researched were more than 80 years old. The oldest fish came from lakes near Pelican Rapids, Minn., including Crystal, Rush, Prairie, Pelican, Lida, Lizzie and Fish.

"We need to start recognizing bigmouth buffalo and other native fish species as the assets they are," Lackmann said. "Hopefully this study can begin spreading awareness for underappreciated fish species and show the state of Minnesota that they deserve protection like many other native fish."

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The bigmouth buffalo is found in 22 states and Canada, but despite an important place in Midwest history (Lewis and Clark harvested them and they have value as a commercial fish) they've been lumped in with invasive species like the common, bighead and silver carp. Harvest remains almost unregulated in the U.S., while Canada gave bigmouth buffalo special concern status in the 1980s.

The study, published recently on the website of the international science journal Nature, was spurred by Lackmann's curiosity and his hunch, along with that of NDSU biological sciences professor Mark Clark, that the fish were much older than previously thought. Existing age data on fish was largely compiled by counting rings on scales, similar to aging a tree, and the typical age of a bigmouth buffalo was believed to be 5 to 20 years. One small study of bigmouth buffalo using otoliths (ear bones) in Oklahoma in 1999 found a maximum age of 26.

Lackmann, a 28-year-old Fargo Oak Grove High School and Concordia College graduate who went to NDSU for post-graduate work, began the study in 2016 by collecting bigmouth buffalo samples from several sources, including bowfishermen who were taking fish from lakes near Pelican Rapids.

The first fish Lackmann aged, using otoliths, was 87 years old.

"It was crazy," he said.

The craziness was far from over. The more fish Lackmann and his fellow researchers aged, the more they found bigmouth buffalo more than 80 years old. In one batch of 26 bigmouth buffalo from Crystal Lake, 25 were determined to be 83 years or older. The other fish was 40 years old.

The fish were huge, including females that were over three feet long and weighed between 25 and 40 pounds. This made them attractive and easy targets for the bowfishermen, who because of recent changes in Minnesota fishing regulations can fish at night with spotlights and during the buffalo's spawning season.

Lackmann, like others he told about his findings, was skeptical. The fish he was aging were commonly six decades or more older than previously established standards.

"People were skeptical because the ages were off the charts. It was understandable. I was skeptical, too," Lackmann said.

So Lackmann and his team used bomb radiocarbon dating to validate their otolith readings. The dating method shows time-specific markers in living creatures that are a result of radiocarbon from atmospheric thermonuclear bomb testing in the 1950s and 1960s. The radiocarbon dating validated the earlier numbers.

"The skepticism was gone. Age validation with radiocarbon is so conclusive," Lackmann said.

The final figures were astonishing. Of the nearly 400 fish aged in the study, five exceeded 100 years and nearly 200 fish were in their 80s and 90s.

According to NDSU, the bigmouth buffalo is now known as the longest-lived freshwater teleost (ray-finned fish) and the oldest age-validated freshwater fish in the world.

"This is a paradigm shift in how we're looking at these fish and should open a discussion about their real value," Lackmann said. "They should not be called 'rough fish,' which carries a negative connotation. They should be viewed as an ecological asset."

The study included four Minnesota watersheds including the Crow, Minnesota, Otter Tail and Pelican rivers. All but one of the 224 fish tested from the lakes in the Pelican River watershed was older than 32 years. Lackmann said 80-85 percent of the fish from the Pelican watershed were over 80 years old (hatched in the 1930s or earlier) and the bulk of the remaining fish were 35-45 years old. The oldest bigmouth buffalo, including the 112-year-old fish, came from Crystal Lake. Lizzie, Rush, North Lida, Pelican and Prairie lakes also had fish hatched before 1940.

Lackmann isn't exactly sure why those lakes seem to have huge gaps in reproduction and why old fish are concentrated in them, but he hypothesized that dams on the Pelican River stopped buffalo from swimming upstream to spawn and muted environmental cues to reproduce.

"I obviously don't know for sure, but there are indicators. There are four dams in the eight-lake sampling area and they were all built between 1936-1938," Lackmann said. "Over 80 percent of our fish from the Pelican River basin were born prior to 1939. That's pretty interesting evidence."

Lackmann hopes his research will lead the Minnesota Department of Natural Resources and agencies in other states to reconsider designating bigmouth buffalo and other native species as "rough fish." He believes the definition leads fishermen to minimize buffalo's importance. Bowfishermen, using boat platforms and high-powered spotlights under liberal harvest laws, have rapidly found bigmouth buffalo to be a premier species to target because of their size and susceptibility.

One other tidbit from the study: Lackmann and his team found unique pigmentation on bigmouth buffalo, orange and black spots, correlate with age. Lackmann said it's a way to roughly estimate age without killing the fish.

"I have to say, the bowfishing guys who collaborated with me on this study are all concerned they are taking fish that are this old," Lackmann said. "Like the rest of us, they didn't know these fish were 80, 90 or 100 years old. They are doing what's allowed under the law. Some of the guys felt bad when I told them the age of some of these fish. I'm hoping this research can lead to some advocacy for these fish and others that are undervalued."