Hank: When you think “long-lived,” you generally think tortoises, redwood trees, and David Attenborough. You don’t usually think fish. Fish are simple creatures that tend to meet their end in some other animal’s mouth, or floating at the top of your home aquarium, you know, if you are bad at fish-keeping. So a hundred-year-old fish is pretty special, and a whole genus full of fish centenarians borders on astonishing.

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These are the buffalofishes: freshwater fish in the genus Ictiobus. These fish are native to the Great Lakes and the Mississippi River, with some species found as far south as Mexico. Buffalofish are not native to Arizona, but they do live there because people put them there more than 100 years ago.

In 1911, Theodore Roosevelt dedicated Roosevelt Dam in his own honor, because that’s the kind of guy he was. And in 1918, the Bureau of Reclamation stocked the newly created reservoir with buffalofish. At some point, the buffalofish made their way from Roosevelt Lake to Apache Lake, another reservoir created by another dam. And they seem to be doing swimmingly there, even though they’re living in a desert that they don’t belong in, in a lake that also doesn’t belong there. But what makes this story weird is despite their fish-out-of-water existence, they’re not only thriving in Apache Lake, they’re also thriving for decades.

See, buffalofish are among the world’s oldest living animals. At least, these ones are. And by “oldest living,” I don’t mean there’s one or two old buffalofish telling all the other buffalofish to stay off the lawn, I mean centenarians are the norm. When you move them to an artificial lake in Arizona, at least. But based on this population, researchers think hitting the century mark is easily possible for at least three of the five species of buffalofish. And it’s not that the other two don’t live that long. It’s that research is still pending. And this isn’t exactly a common thing in animals. There’s only one other animal genus we know of with three or more species that have a maximum age of over 100. The other one is a marine fish, the rockfishes.

What’s more, buffalofish also don’t seem to suffer from the effects of age. They do not seem to physically decline the way that humans do; the bigmouth buffalofish kind of gets better with age, which seems grossly unfair really.

In fact, a 2021 study found that older bigmouth buffalofish tend to have improved immune function and lower stress levels compared to their younger counterparts. This newfound knowledge about how fish can sometimes surpass the lifespan of humans, when we have the whole of medical science at our disposal, comes to us courtesy of citizen science. The data was collected by citizen scientist-anglers fishing in Apache Lake, and we love to see it.

It turns out Apache Lake is a better place to do this research than in the fish’s native range. That’s because buffalofish are at risk of extinction in their native range thanks to overfishing. And it’s hard to study longevity when fish get caught and eaten before they have a chance to reach the end of their natural lifespan. Apache Lake is remote and hard to reach, so the buffalofish have been able to live there mostly undisturbed. For this study, published in Nature Scientific Reports in 2023, anglers caught, photographed, and released most of the fish, and donated a few others to scientists. For the 23 fish that were donated, the researchers could establish an age by looking at the otolith, a structure in the inner ear that forms rings as it grows like trees do.

Almost all of the specimens scientists dissected were older than 80 years. And the researchers think some of them are the exact individuals that were stocked in Lake Roosevelt in 1918. The photographs were also helpful in establishing an age range for Apache Lake’s buffalofish, since fish older than 40 have “age spots,” and fish older than 80 have more spots that are more well-defined. This is, of course, less precise than looking at the otolith, but the fish gets to swim another day.

What’s also super odd is that all of the fish captured were old — 40 years or older. There don’t seem to be a ton of younger individuals. Spawning has not been documented in Apache Lake, even though the scientists checked the individuals they dissected and, like, everything seemed to be in working order. So the researchers aren’t sure if the fish are breeding or not, and if not, why. Though it’s worth pointing back at the earlier “neither the fish nor the lake are supposed to be there” thing to suggest that maybe the conditions really aren’t right for bringing little buffalofish into the world.

The study’s authors feel that their results are a representative sample of the individuals in the lake, and not just something that happened by chance – the fish really do live to be that old. Not only did this study uncover some unknown information about buffalo fish, but it also cost very little to conduct, thanks to volunteer anglers. So this has not only taught us something remarkable about longevity in freshwater fish, but also about the power of citizen science.

So if you’re good with a rod, maybe it’s time to plan a vacation in Arizona.

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