One Monday morning, at the Shinnecock Canal, a thin strip of water that separates two Long Island bays, locals found an apocalyptic sight.

Hundreds upon hundreds of dead fish were floating on the canal’s surface, so dense that one man told local news that “you could’ve walked across the water.”

These were bunker fish, which are also called menhaden or pogies. They’re a flat fish, that never grow too large—no more than about 15 inches. They’re one of those fish that play a key role in the aquatic food chain: they’re prey to many of the larger fish that humans tend to favor as food.

And it’s likely that a school of some larger fish is responsible for this massive bunker fish die-off. Predator fish could have chased the menhaden into this canal, where they crowded together in a dead end, quickly sucking out all the oxygen from the water and suffocating.

Not all of these fish will go to waste: local fishermen are gathering them to sell as lobster bait, and any bird that comes across this bounty will have a feast to contemplate.