Menhaden are small, silvery fish that swim in huge schools along the Atlantic and Gulf coasts of North America. You've probably never eaten one, because they're too bony and oily for most people's taste, but menhaden might be the most important fish you've never heard of.

These fish are ecological powerhouses. A single adult menhaden filters up to four gallons of water per minute, eating tiny floating plants and animals called plankton. When millions of menhaden swim through coastal waters, they act like a giant cleaning system, keeping the water clear and healthy. Larger fish like striped bass, bluefish, and tuna depend on menhaden as a major food source, which is why fishermen call them “the most important fish in the sea.”

Humans harvest enormous quantities of menhaden, not for eating directly but for processing into fish oil, fertilizer, and animal feed. The fish oil extracted from menhaden contains omega-3 fatty acids that end up in dietary supplements and pet food. For over a century, menhaden have also been ground up to make fertilizer that helps crops grow.

Indigenous peoples taught early colonists to bury menhaden in their cornfields to enrich the soil.