Fish Facts: The Questions Kids Ask About Fish, Answered With the Science

A herring talks to its school by blowing streams of bubbles out of its rear end, and the scientists who proved it won the 2004 Ig Nobel Prize in Biology. There are more than 33,000 kinds of fish, and the questions about them are the same everywhere: do fish sleep, do they feel the hook, can they hear you talking, why does a fish out of water die? Each answer changes something you do when you have a fish on the line, in your hands, and back in the water.

Rainbow trout kept out of the water for 60 seconds survived 28% of the time; trout returned with no air time survived 88%. Ten seconds is the number to teach a child before the first cast.

Start here

Senses and feelings

• Do fish feel pain? — trout have 22 pain receptors (nociceptors) on the face and head, scientists argue about what the fish feels, and hook location decides who swims away.
• Do fish have feelings? — stress hormones, a fish that passed the mirror test, and why a fight is an escape, not anger.
• Do fish have brains? — the three-second memory is a myth; goldfish learned to drive a tank on wheels, and carp remember a hook for days.
• Do fish hear? — no ears you can see, yet a catfish heard a whistle from 213 ft (65 m); your voice barely reaches them, your footsteps do.
• Do fish see water? — no more than you see air; the whole sky squeezes into a 97-degree window above the fish, which is why you crouch.

How a fish works

• Do fish sleep? — yes, without eyelids; a zebrafish sleeps 58% of the night, and a bullhead lies on the bottom tilted like a parked bike.
• Do fish drink water? — freshwater fish almost never do, saltwater fish drink all day, and the difference explains the livewell.
• How do fish breathe? — gills, countercurrent blood flow, and the table of how much oxygen water holds at every temperature.
• Do fish drown? — not the way we do, but they suffocate, and dragging a fish backward to “revive” it is the wrong move.
• How do fish reproduce? — eggs by the thousand, a father bass that guards the nest, and a perch that lays a 7 ft (2 m) ribbon.
• Do fish have bones? — most do, sharks do not, and 16 kinds of Antarctic icefish have blood as clear as water.
• Do fish get cold? — a fish is as cold as its water, some carry antifreeze, and winter bass still swim and nibble.

The odd ones

• Do fish have teeth? — nearly all do, some in the throat; the sheepshead has molars, and pike keep theirs all summer.
• Do fish have tongues? — a bony fold with no taste buds, sometimes with teeth on it, once replaced by a parasite.
• Do fish fart? — herring do, on purpose; most other fish burp their gas out, and a shark gulps air to float.

Which facts are worth repeating at the water?

Two rows change how you fish. The oxygen row explains why a bass sits deep on a hot afternoon and why a livewell needs a pump: water at 90 °F (32 °C) holds about half the oxygen of water at 32 °F (0 °C). The water-temperature chart has those numbers for 26 species. The air-time row is the habit good anglers share: unhook the fish in the water when you can, take the photo over the water, and count to ten. A 2015 review (Cook and colleagues) is cited for a ten-second limit, and the catch and release page shows the hold and the ten seconds step by step.

What do you tell a child who asks?

Four of these questions come up in the car, and each has an answer short enough for a red light.

1. Does it hurt the fish? The fish has pain receptors and a stress response; whether it suffers the way we do is argued over by scientists (Sneddon 2003 against Rose 2014). What is settled is what helps: a hook in the lip, a short fight, a fast release with wet hands.
2. Can the fish hear us? Barely, if you talk. Almost all of a voice bounces off the surface. Feet stamping on a dock and a tackle box dropped in a boat go straight into the water, so the rule is quiet feet, not quiet mouths.
3. Why do we put it back? Because it grows, and because it learns. A carp that has been caught avoids the hook for days, which means the fish you release today is the smarter fish you catch next summer.
4. Why can’t it breathe up here? Its gills need water flowing through them. Out of the water the thin gill plates stick together and the oxygen stops. That is where the ten-second count comes from.

For the first trip itself, the fishing for beginners guide covers the rod, the bait and the fish to start with.

For the fish under your bobber, the species profiles cover what each one eats and where it lives. For what wind, cloud, rain and the moon do to the bite, read fishing weather.

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Your first fishing trip, from the store aisle to the first fish

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• Walk out of the store with the right rod and nothing extra: the $85–100 kit, item by item
• Know if you need a license, in 13 states, and the places where nobody needs one
• What to do when the bobber goes under, and the ten-second rule for letting the fish go

Every line from the beginner pages on fishing.info and the 246 sources behind them, the U.S. Fish and Wildlife Service and the Missouri Department of Conservation among them.

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