From Saskatchewan to Mexico, buffalofish have been swimming under scientists’ radar. They’re a group of non-game fish, relatively difficult to catch, and not considered economically important to the regions they live in. Compared to other freshwater fish, very little is known about different species of buffalofish and their behaviors.
It was once thought that buffalofish only lived up to 26 years in the wild. Then in 2019, researchers identified a centenarian buffalofish in Minnesota. Now in a new study, scientists caught and analyzed specimens from Apache Lake, Arizona, and confirmed that three different species of buffalofish there can live to be more than 100 years old—and could possibly live for many years more, based on their health. That makes them only the second animal genus, after the marine rockfish Sebastes, on record with three or more species that can live past a century. The discovery could change how we manage buffalofish populations across North America, and lead to more experimental anti-aging research in the future. The findings were published in October in the journal Nature’s Scientific Reports.
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To pinpoint the ages of these fish, researchers focused on otoliths, the stone-like structures found in the ears of 97 percent of fish species. “What’s really interesting about otoliths, and what makes them so valuable for age analysis, is that they put down rings as they go through slow growth periods,” says Alec Lackmann, an ichthyologist at the University of Minnesota Duluth and lead author of the new study. His team examined thinly sliced sections of the otoliths to estimate fish ages. They double checked their findings with radiocarbon dating, revealing signs that corresponded to historical events and environmental changes in the area. For example, samples from fish that lived through the 50s and 60s contained unique radiocarbon signatures from when the US was testing nuclear bombs in the West.
The smallmouth buffalofish the researchers found in the lake ranged from 11 to 101 years old; the black buffalofish were 106 to 108 years old; and the bigmouth buffalofish were 85 to 105 years old. What makes the fishes’ longevity even more remarkable is that they aren’t native to Arizona waters, Lackmann says—the three species were introduced to the state in 1918, likely from Iowa. So, based on the results of the study, it’s likely that some of Arizona’s first buffalofish are still in Lake Apache today.
“I found the new study very exciting and novel in that it was the first to look at multiple species of buffalofish,” says Jeff Sereda, a manager of ecological and habitat assessment at the Water Security Agency in Saskatchewan, Canada. Sereda has studied buffalofish and has previously collaborated with Lackmann, but was not involved in the latest research. “We don’t know what the fishes’ actual upper limit for age is,” he says, and that has “completely turned up our understanding of these species on its head.”
Before, biologists thought buffalofish populations were relatively stable wherever they existed. But the fact that most of the tested fish were excessively old indicates that they might be more at risk of decline than we thought, Sereda explains. If they’re living for so long, but numbers are stable, it’s a sign that they’re barely reproducing. Think of it like the declining birth rate among people in Japan, which is causing the average age of the population to rise and the overall size of the population to shrink.
Another aspect of buffalofish that isn’t well understood is their reproductive behavior. Researchers in Saskatchewan haven’t found evidence of new young buffalofish in about 40 years, Sereda says. The fish spawn sometimes but don’t survive to the juvenile stage. Buffalofish remain fertile through old age, even after decades of not spawning any young, Sereda adds. We just need more research to tell whether this is how they survive—living long lives and successfully rearing very few young—or if there’s something amiss.
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Getting a clearer picture of how buffalofish in different waters live and reproduce can give us a more accurate idea of how they’re faring. They’re classified as “special concern” in Canada, in part because of the lack of data. While a few species have special conservation statuses in the US—bigmouth buffalofish are endangered on the Pennsylvania state list— researchers don’t have a good grasp on the population sizes or trends in most places where buffalofish are found. Without that information, it’s hard to know what their exact needs are.
“There’s such mystery surrounding buffalofish,” Lackmann says. In the future, he would like to study the otoliths of other buffalofish of the same genus, including one species in Mexico. Getting a better grasp of how their genes contribute to their impressive lifespans could also provide insight into how vertebrates postpone aging, he adds. “It’s incredibly fascinating.”