When big fish that dominate the seas suddenly disappear, small fish take over—and stay on top for hundreds of millions of years. At least, that’s what happened after a mass extinction some 359 million years ago. Thanks to overfishing, scientists worry it could be happening again.

That grim prediction comes from a new study in Science analyzing the effects of something called the Hangenberg Event—the closing chapter of the fourth of those five mass extinctions you’re always hearing about—which blotted out 97% of vertebrate species.

Up until that point, a diverse cast of gigantic fishes — many the size of school buses — ruled the seas, gobbling up small fish. After the mass die-off, though some big fish lingered, nearly all eventually died out. The creatures that repopulated the seas instead were much tinier than before, many of them shorter than a ballpoint pen. For another 40 million years, these little guys overran the oceans…

…Analyzing more than 1,200 fossils from before and after the Hangenberg Event…researchers concluded that natural selection was solely responsible — a finding that has ominous implications for how humans are warping ecosystems today…

Humans are now doing something unsettlingly similar…Many of the 80 million tonnes of wild-caught fish…we eat each year are the big ones—cod, tuna, halibut, to name a few. Others that don’t show up on your sushi menu — sharks and rays, for instance — often die tangled in nets meant for other species.

“The point is that losses of this magnitude take millions of years to recover from and alter ecosystems long-term no matter how the deaths occurred,” says Professor Lauren Sallan.

Growing up subsistence fishing along the sluthern New England coast, I find overfishing, malfishing, contemptible and stupid. One of those illnesses only capable of solution by international compact and regulation. Abhorrent, of course, to the anarchy of what passes for Congress, lately.

Yes, I can survive on anchovies instead of sea bass steaks. But, why should the choices made by greedy corporate fishmongers govern the choices remaining to consumers like me?