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Many different animals live in the rivers, lakes, and oceans of our planet, but it may
surprise you to find out that not all of them are fish!
To be a fish, an animal must be a vertebrate, meaning it has a backbone, and it must live
in water for its entire life.
Most fish, but not all, have scales, and fins, and use gills to absorb oxygen from the water
around them.
Let's take a look at some of our favorite aquatic creatures and find out whether they
are fish or not fish!
We'll start with a familiar friend: clownfish.
Clownfish are small colorful fish that have symbiotic relationships with anemones.
The clownfish hide from predators inside the anemone's stinging tentacles, and in return
the clownfish chase away any fish that want to eat the anemone.
Are they fish, or not fish?
Fish!
Clownfish are real fish.
They have backbones and live in the water all their lives.
They also have gills and fins.
Oh look!
Seahorses!
These little creatures live in shallow tropical or temperate waters, often in seagrass beds
or coral reefs.
But are they fish, or not fish?
They're fish!
Seahorses may not look like what you think of as a fish, but they have backbones and
fins, breathe through gills, and live in the water their whole lives - and that means they
are fish.
Next up, starfish.
They can live in deep or shallow water, but all starfish live on the sea floor.
Starfish usually have five arms, but some species can have as many as 24.
So: are they fish, or not fish?
Not fish!
Starfish are invertebrates, with no bones at all.
Instead, they are Echinoderms, and belong in the same group as sand dollars and sea
urchins.
Hey, is that a shark?
There are more than 500 different species of shark in earth's oceans, ranging from the
small to the very large.
Sharks are recognized as amazing predators all over the world, but do you think sharks
are fish, or not fish?
Fish!
Sharks are vertebrates, although their skeletons are made of a flexible material called cartilage
instead of bone.
They also live in the water, have fins, and use gills to breathe, which places them firmly
in the fish category.
Over here we have a cuttlefish.
Sometimes cuttlefish are called the chameleons of the sea, because they can change the color
and pattern of their skin.
They use this ability to communicate with other cuttlefish and to camouflage themselves.
Cuttlefish are very smart, but are they fish, or not fish?
Not fish!
Cuttlefish are cephalopods, a group of invertebrates that includes octopus and squid.
All cephalopods have long, flexible tentacles or arms.
Here's a set of speedy swimmers - penguins!
Penguins live almost exclusively in the Southern hemisphere, particularly in the waters surrounding
Antarctica.
They eat fish, krill, squid, and other ocean creatures.
Are penguins fish, or not fish?
Not fish, of course!
Penguins are birds, even though they can't fly.
They spend about half of their lives in the ocean, but they must surface to breathe and
they lay their eggs and raise their chicks on land.
Oh look, there's a ray!
There are more than 500 different species of rays, including stingrays, manta rays,
and eagle rays.
When they swim they almost look like they are flying through the water like bats.
Do you think rays are fish, or not fish?
They're fish!
Just like sharks, rays have skeletons that are made of cartilage instead of bone, but
they do have a backbone, live in the water all their lives, and breathe through gills,
which means they are definitely fish.
Next up we have jellyfish.
Jellyfish can be found in waters all over the world, from deep dark oceans to sunlit
seas.
Most jellyfish are made up of a soft, umbrella-like body called a 'bell' and long, stinging tentacles
that they use to catch prey.
Our question is: are they fish, or not fish?
Not fish!
Jellyfish do not have bones - they don't have eyes, a heart, or a brain, either!
They are a kind of invertebrate called Cnidarians, and other animals in that group include corals
and anemones.
Time to visit some aquatic creatures that are much smarter than a jellyfish - dolphins!
Playful and intelligent, dolphins are a friendly sight.
They travel in groups call pods, eating eels, squid, fish and shrimp.
Are dolphins fish, or not fish?
They are not fish!
Dolphins are mammals: although they spend all their lives in the water, they need to
come to the surface to breathe air and they feed their babies milk.
Dolphins have a special sense called echolocation that they use to help find their way underwater.
They will make high-pitched clicks, and the sound waves will reflect off of any objects
ahead, like an echo.
Echolocation lets dolphins detect objects the size of a golf ball about 100 meters away!
Let's try one more: eels.
Long and narrow, they might be mistaken for underwater snakes if you didn't know any better.
Most eels live in shallow ocean waters, often tucked away in a favorite hiding place, and
most eels are predators.
The question, then, is are they fish, or not fish?
Fish!
Eels are vertebrates that live in the water their whole lives and they breathe using gills,
and that means that despite their appearance, they are in fact fish.
Unlike most fish, eel do not usually have scales, just smooth skin.
There are more than 33,000 different species of fish on Earth, and many of them look peculiar,
but they all have a few things in common.
I hope you enjoyed learning about fish today, and thanks for playing fish? or not fish?