Even history’s minor events can have momentous consequences, as I saw yesterday while bicycling along the C&O towpath upstream on the Potomac River from Sycamore Landing.

Just past the sod farm, my nose connected with a stench that only a vulture could love. Did it come from the river? A fish kill, or perhaps a dead deer on the shore?

It turned out that the odor’s source was the normally dry canal bed, where puddles of stagnant water still remained from the recent flood.

I stopped to take a look. There among the rotting tree limbs and clumps of vegetation, I saw something breaking the water’s still surface. I also heard slurping sounds.

In the shadowy light, I could make out the opening and closing of fishes’ mouths, like so many animated rubber bands. They belonged to carp, maybe 14 to 16 inches long. Oblivious to me, they were focusing on the one thing that mattered: getting air.

Carp are famous for their ability to live in the most stagnant, oxygen-depleted water. Conditions here must have been getting desperate.

Meanwhile the larger carp had already succumbed. Their thick yellow-gold bodies, covered with flies, lay amidst the rotting debris. Some had already been deposited on the shore by the receding water. One carcass was  so carpeted by yellow maggots that it was barely visible under the squirming, pulsating mass.

Piecing together the evidence. I tried to reconstruct what happened, fancying myself a little like the young Charles Darwin in the Voyage of the Beagle, making brilliant connections between things he saw and the natural processes that produced them.

The towpath on which I was bicycling forms a kind of levee between the Potomac and the canal. At Cabin Branch, which enters the river just upstream from the dying carp, the towpath dips down. There, I surmised, the recent floodwaters poured into the normally empty canal channel, taking the fish with them.

Had the carp been swept into the canal involuntarily? Or were they seeking refuge from the swift current?

Also, why did I just find carp? I didn’t see any signs of bass, catfish, sunfish, or other common Potomac River species. Are these other fish, which are more at home in running water environments, better able to find protective nooks and crannies to tough out the swift currents? Do carp, the quintessential fish of lakes and ponds, lack this ability?

As the waters receded, the carp’s temporary refuge became a prison, and ultimately a death trap. In a few days, perhaps a week at the most, the smaller fish I saw gulping air will also near their end. Raccoons will arrive for a feast, and perhaps a fox, or even snapping turtles. But their appetites will be dwarfed by the magnitude of this protein windfall. Ultimately, the maggots, bacteria, and other creatures will finish off the job.

I will return in a few weeks. By then, all signs of this mass death probably will have vanished. It will have been just another little event down by the river, quickly forgotten. But for the carp, it was the end of the world.