6 Fascinating Facts About Fish and Their Incredible Sense of Smell

Can Fish Smell? Yes — And It’s Way Cooler Than You Think

We’ve all heard the old tale that sharks can smell blood from a mile away. Turns out, that’s only true for a few species like the lemon shark. But it does open up a really interesting question: can fish smell at all?

Short answer? Absolutely. But their version of “smelling” works a bit differently than ours.

Let’s break it down — with some fun facts and real-world insights I’ve learned from diving into fish behavior (and yes, trying to outsmart them when fishing!).

How Fish Smell Without Noses

Fish don’t have noses like we do — instead, they have little openings called nares near their eyes. These don’t help them breathe (that’s what gills are for). They're purely for detecting chemical signals in the water — and that’s where the magic happens.

Water flows through the nares into special scent-detecting organs. These organs are sensitive to all kinds of molecules: food, other fish, danger, even the chemistry of a familiar river.

For example, salmon can literally smell their home river. After years in the ocean, they’ll navigate back to spawn, relying on their internal GPS (Earth’s magnetic field) to get close, and then using smell to pinpoint the exact stream they were born in. Amazing, right?

Some Fish Can Smell Without Moving

Most fish need to swim to get water flowing through their nares, but others — like zebrafish and salmon — don’t. They’ve got tiny hair-like structures called motile cilia that help push water through their scent receptors even when they’re still. It’s like having a built-in fan constantly wafting smells toward their brain. Handy for spotting predators early!

Not All Fish Smell Equally

Fish have different scent-sensing organs depending on the species. For instance, channel catfish have up to 140 folds in their olfactory system — making them smell experts. Pike? Only about nine folds. That’s a big difference.

Catfish can detect some substances in concentrations as low as one part per 100 million. American eels go even further — one part per trillion! That’s like finding a single drop of dye in 20 Olympic-sized swimming pools.

Some fish, like bullheads, even use scent to figure out social rank. They can tell who’s “in charge” in their group just by sniffing out chemical cues. Think of it like a royal perfume only the queen wears.

Baby Fish Can Smell Home, Too

In Australia’s Great Barrier Reef, baby coral fish like damselfish are often swept far away by ocean currents. But within just 20 days of hatching, many of them find their way back home — purely by following scent trails in the water. Not sight. Not sound. Smell.

What Fish Smell — And Why It Matters

Fish are especially tuned in to amino acids (which often signal food nearby) and bile acids (which signal that feeding happened recently). If they smell bile acids in the water, they know it might be a good hunting spot. They're also capable of recognizing other fish — even from different species — just by their “chemical signature.”

Some fish can even smell ATP — the energy-carrying molecule released when prey like zooplankton move around. Zebrafish have a special receptor (A2c) just for this. It’s like having a scent radar for dinner.

Why It Matters for Us (and the Fish)

Unfortunately, climate change is messing with this finely tuned system. As oceans absorb more CO₂, they become more acidic. In lab tests, fish in acidic water didn’t respond to the scent of predators. That's scary — not just for them, but for ecosystems and the billions of people who rely on fish for food.

One Last Tip (Especially if You Fish)

Remember, fish don’t smell airborne scents — only what dissolves in water. So that stinky bait that makes you gag? It might not do anything for the fish unless it releases the right water-soluble compounds.

Some fish, like catfish, will follow a scent trail from 100 yards away. Others, like bass, rely more on movement and visuals than smell. So if you’re fishing, tailor your approach to your target species’ senses.

The Bottom Line

Fish absolutely can smell — and their sense of smell is wildly complex and fine-tuned. From finding food to navigating home to avoiding danger, it's a vital part of how they survive. And the more we understand it, the better we can care for our oceans and the creatures in them.