So Kuhajda and his team donned waders and dragged a large sieve through the muddy pools, collecting 64 of the small, iridescent killifish to take back to the Tennessee Aquarium, where they maintain an “ark population” as a hedge against their possible disappearance in the wild.

“If we hadn't rescued these 64, this entire genetic population of Barrens topminnows would have disappeared,” Kuhajda said. “This species would have been one step closer to extinction, and it's not many steps away now."