The trickle — little more than a few big mud puddles — was one of the last bodies of water left with a population of Barrens topminnows, and it was drying up.

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.