How Do Fish See? How Do Fish Sleep? How Do Fish Breathe?
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This is But Why, a podcast for curious kids from Vermont Public Radio. I'm Jane Lindholm. On this show, we take your questions and it's our job to find interesting people to help answer them.

Here's a taste of what we're going to tackle today. Do fish drink water? Why do fish swim when they're asleep? How do fish see underwater without goggles? They swim in the ocean, in lakes and rivers, sometimes even in tanks in your living room. We're talking all about fish this week.

Should we go look at fish? To get a really good look at some fish, I visited the New England Aquarium in Boston and spoke with Jo Blossie. She's in charge of education and training at the aquarium. So we usually have around 1.3 million people coming to the aquarium. We have people that live right in our own neighborhood, and we have people that come from all over the world. That's a lot of visitors.

And when they visit, they get to see lots of fish and other aquatic animals like penguins, sharks, and squid. But we asked Joe to answer your questions about fish. Our first one today comes from Lila. I'm five years old. I live in Pittsburgh. I want to know...

How did the first fish get in the ocean? How did the first fish get into the ocean? So a long, long, long time ago, over 5 million years ago, even before the dinosaurs, there were lots of animals living in the ocean. Things like jellies and other animals that didn't have backbones. So there were all sorts of different animals in the ocean.

But over time, as they changed and they evolved, little by little, they started to grow backbones like we have. And they started to develop a bony structure in their head, almost like a skull. So these sort of animals evolved over time. And about 531 million years ago, scientists think that the first sort of

fish-type animal arrived in the ocean. And then over time, they evolved and evolved and evolved into sort of four big groups of fish. Two of those big groups are now extinct. You can't find them on the planet anymore. But the other two sort of grew into the bony fish, fish that have bones in their skeletons.

And then the other group grew into like the sharks that have cartilage as their skeletons. So some sort of fish have been around even longer than the dinosaurs. And we still have some of their relatives around today, but most of the relatives aren't around anymore.

What are the two kinds of fish that aren't around anymore? How are they different? Some of them have like big armored scales and some of them were just really different than the animals that we have in the ocean now. How many different kinds of fish are there? There's lots and lots and lots of them. A lot of them actually live in freshwater. So you have to remember that there's freshwater fish that live in ponds and rivers and streams. There's also animals that live in saltwater, like the ocean. So there's lots and lots and lots of different kinds of fish.

And if you want to learn about anadromous fish who can live in salt water for part of their lives and fresh water for other kinds, we think of salmon like that sometimes, but also alewives, you should listen back to our episode that we did on the coast of Maine. And we talked about anadromous fish and lobsters and snails. So listen back to that episode. But today we're talking about fish. So here's the next fish question.

Hi, my name is Emily. I'm seven years old. I live in San Carlos, California, and my question is, how do fish breathe underwater? My name is Eleanor from Battleford, Vermont, and I'm five and a half years old. And why can't fish breathe out of water? Why can't fish breathe out of water? Hmm.

Most fish use gills and they call gills to breathe. So again, we like other animals need oxygen. So we breathe in air and our lungs help us get oxygen out of the air. Fish need oxygen and most of them get their oxygen from the water. So they have something called gills and those gills help them absorb the oxygen from the water and that oxygen can then go into their bloodstream.

And then that blood can go throughout their body and that oxygen get to all the places that need it, like your muscles and brain and things like that. There are some fish that actually breathe out of the water. So one of my favorites is called a mudskipper. And mudskippers, what they do is they still have gills like other fish, and they make sure that they have a little pocket of water. They keep their gills nice and wet, but then they can actually climb out of the water. We have some at the aquarium. They're pretty fun to watch.

And then there's also fish called lungfish that actually breathe in big gulps of air or actually go up to the surface of the water and breathe that way as well. If the fish that breathe underwater, that use the water and get the oxygen from the water, are still breathing oxygen, why can't they just get the oxygen out of the air? What is it about gills that makes it so they can't do that?

So the way that gills work is that gills contain blood vessels and blood that comes very, very close. The water helps the oxygen flow over the gills. So if the gills dry out, they're not going to be able to work as well underwater. Just like if you go underwater and you breathe, you can't breathe underwater because your lungs aren't designed to work that way. Your lungs are designed to

with your blood vessels to get the oxygen out of air instead. So it really depends on what kind of animal you are and where you are supposed to be. Okay, here's a very specific question, but kind of related to what we were just hearing about. Hi, my name is Juniper, and I'm six years old, and I'm from Essex, Vermont. And my question is, if you just put a fish's head under the water and on its tail, would it still survive?

This is sort of a tricky question. So most fish breathe underwater. So if you put their head underwater along with their gills, which is how they breathe, they would be able to breathe. But if their tail was out of the water, they might not be a very happy fish. They need their tails to move, to find food, maybe to find a place to hide or a place to sleep. So it could probably breathe, but it might not be very happy.

There are some fish, though, that actually breathe air. So if you put their head underwater, they might actually not be able to breathe. But for most fish, they'd be able to breathe okay, but they might not be very happy.

Do their bodies need to stay wet though? I mean if you had just the head underwater and the rest of the fish got dry, would that be a problem? That's true. They're probably having really dry skin if you're a fish probably wouldn't be a very happy thing. We actually do surgery on fish here at the aquarium. Sometimes fish get sick just like we do and we can do surgery just like they would do for people. And one of the things they try to do is make sure that the skin of the fish stays wet even if they're out of the water.

So my bet is, yeah, that skin probably wouldn't be very happy and that the fish would rather that skin stay nice and wet. My name's Aubrey, age six. I come from Merced, California. And my question is, how do fish get diseases?

So speaking of surgery, how do fish get sick? Yeah, so fish can get sick just like we can. They can get bacteria infections or viral infections or fungal infections. They can get tumors or all sorts of things. Some of it comes from their environment, just like us. Sometimes they might get sick if they come into contact with another fish that might be sick as well.

So they can also get sick if there's something in their environment that's making them not feel well. So if there's pollutants or if there's something that's stressing them out, then they might be more likely to get sick just like we can. So if you have a fish in a fish tank, if you keep a pet fish and it gets sick, is that probably because you're not keeping the water as clean as it should be or something like that? Yeah.

There could be lots of different reasons why a fish could get sick. Sometimes they just get sick. But just like people, there's a whole bunch of things you can do for sick fish. You can give them medicines or you can put things in their fish tank to make the water a little bit better for them. We give some of our animals medicine to make them better, whether it's in a pill or a shot. Or sometimes we can do surgeries if we have to.

That must be interesting to watch, fish surgery. So you take them out of the water, but you keep them wet so their scales stay wet, and then somebody who's a veterinarian who's trained in fish surgery does the surgery? Absolutely. And...

Animal medicine is very similar to people medicine. So if we have to do a surgery, one thing that we can do is very carefully put them to sleep, just like they would for a person, so we can anesthetize them. So that way they don't feel any pain, and that way they can stay nice and still, so we can do the surgery. So we have veterinarians and biologists and everybody working together to do all sorts of surgeries. And at the aquarium, we've done surgeries on seals and penguins and turtles and pharmas.

fish and a lot of different things. So we have really smart veterinarians at the aquarium. Sometimes people say there's so many fish in the ocean. So if you extend that to sick fish, why would you do surgery on a fish instead of saying, well, this fish is sick. I guess we'll get a new one.

Yeah, I mean, the fish at the aquarium, they're underneath our care. So we want to take the best care of them as possible, just like you might with a pet at home. We don't think of them as our pets, but we're thinking of them at the aquarium as something that we want to make sure that we take really great care of. So we do everything that we can to make sure that the animals are happy and healthy here. Fish surgery sounds pretty cool.

It's probably not something that's done by the veterinarians in your neighborhood. When pet fish get sick, sometimes there isn't anything that can be done to help them. A place like an aquarium has a lot of unique species of animals, and they have a lot of scientists working there to keep the animals happy and healthy. Some of you might wonder why these animals are kept in captivity instead of living in the wild, and that's something I asked Joe about.

She says aquariums and zoos are important because they allow people to see animals and fish that they might not be able to ever see in the wild.

Here at the aquarium, we have animals from all over the world. We have three different kinds of penguins. We have anacondas from South America. Those are snakes. Those are snakes, yes. Yes, we have lots of different animals, not just fish at the aquarium. We have penguins and sharks and turtles. And some of the animals that we have here were either born here,

or were injured in the wild, like two of our sea turtles. They were rescued by the aquarium many, many years ago, and we rehabilitated them. We made them better, but they weren't going to be able to go back because they wouldn't survive in the wild. So we gave them a really good home here.

And then some of the animals, again, were born here. And we know that the animals are doing really well if they decide to have babies. And we have lots of babies born at the aquarium every year. But I think aquariums are really great because they get to show –

Animals that people don't normally get to see, and they get to learn a little bit about how we impact animals in the wild. Even something as simple as eating seafood in New England, depending on what kind of seafood you might be eating, might impact an animal down in Costa Rica, like sharks. So it's important that people can understand that we're all part of one big planet and that we all rely on each other and we're all connected. And I think zoos and aquariums get to show people how we're all connected.

Coming up, we'll learn about how fish see, how they sleep, and how they're born. This is But Why, a podcast for curious kids. I'm Jane Lindholm. Today, we're at the New England Aquarium in Boston with the education and training manager, Jo Blossie. She loves teaching visitors all about the cool creatures you can see in the giant tanks at the aquarium. And today, she's answering your questions about fish.

Here's a fun one from Bennett. I'm four years old and I live in San Carlos, California. And my question is, how do fish see underwater without goggles? How do fish see underwater without goggles?

So animals have eyes that are built in a way that is best for their environment. So your eyes are designed to see in air and that's the way that they work best. So if you swim underwater with no goggles, your eyes can't see really well. So what happens when you put on goggles, there's a little teeny tiny bit of air that's trapped in the goggles with your eyes so you can still see underwater.

Now, fish don't need goggles because their eyes are designed to work underwater. They still have the same parts that you do. There's a cornea and an iris and a pupil and the way that the light gets in and bounces around and then transmits a signal to their brain so they can see things. And some fish can actually see really well considering they're a fish. But their eyes are designed to work much better in a water environment rather than an air environment.

One of the reasons that humans blink is to keep our eyes wet. So do fish need to blink at all? They don't because fish don't have eyelids. So no blinking necessary. Whoa, can you imagine not having to blink? That's amazing. In fact, it's making me blink just to think about it. Your body won't actually let you keep your eyes open for too long. It makes you blink automatically without even thinking to keep your eyes nice and wet.

Now, close your eyes and think about sleep. We got two questions about how fish sleep. The first one comes from Emma, who was three and three quarters when she sent us this question from her home in Astoria, New York. Why do fish swim when they're asleep? Hi, my name is Soria. I'm from Ogden, Utah, and my question is, how do fish sleep?

Some fish will swim when they're sleeping. A lot of times those types of fish need water to move over their gills or in their mouth and over their gills to breathe. So some fish will, even if they're very slowly,

moving um it can still breathe while they're swimming but not all fish have to swim to sleep or sleep to swim there are some fish they're called parrotfish they make themselves a little mucus cocoon along a coral reef almost like a little sleeping bag and they can sleep in there for the night so they actually stay very still that way they can hide from predators that little mucus sleeping bag um

allows predators, they can't smell them if they're in the area. So those little sleeping bags help them sleep throughout the night. So some fish will slowly swim while they're sleeping. Others actually stay very still. I'm picturing a mucus sleeping bag. That sounds pretty gross. Yeah, it does. It sounds kind of slimy. Not something I want to sleep in, but parrotfish like it really well.

Hello, my name is Mason and I am eight years old. I am from College Station, Texas. And my question is, do fish drink water? Do fish drink water? So this is a good question and it's a little complicated to explain, but I'm going to try.

So animals have a balance of salts and water inside our body. And that needs to be in the right, both water and the salt needs to be in the right amount in order for us to move and to breathe and to live. So we do a lot of work to make sure that that balance of salt and water is what it should be. So we eat and we drink and our skin keeps lots of water inside us. So our balance of salt and water stays pretty good.

For fish that live in water, they also need to keep the balance of salt and water inside their body the same.

So if you are a fish, though, and you live in salt water, if you live in ocean water, the inside of your body is less salty than the water you're swimming in. And water likes to go where it's more salty. So water, because it's less salty and it's more salty outside of the fish, this water inside a fish's body that lives in the ocean wants to leave. And fish skin is kind of leaky.

So water can actually come out of the fish's body. So because they still need that balance of water and salt inside their body to stay the same,

Saltwater fish that live in the ocean do have to drink water. So because water is leaving their body, they need to drink more water to have water stay in their body. Now, the only water they have to drink is saltwater. So they have special ways of getting rid of all the extra salt that they're drinking with that water. But some fish, like fish that live in the ocean, do have to drink water.

I would have thought all fish drink water. I mean, you see them opening their mouths, and if they're taking in food, aren't they just constantly sort of...

Isn't water going in and out at all over them all the time? Well, water is definitely going in and out. And a lot of times that opening and closing of their mouths is them breathing. They're moving water over their gills so they can get more of that oxygen. And they do get some of the water from the food they drink. They can also absorb water over their mouth and their gills. So there's water that's coming in and out of their body all the time. They're not even thinking about it.

But they do need to make sure, again, that that balance of salt and water in their body is just right. Hi, my name is Adeline. I am eight years old. I live in East Montpelier, and my question is, do fish have ears? Do fish have ears? Not like you and I do. So we have lots of outside parts of our ear. Fish do have ears, but they're actually inside their head, so you can't see them. And they have little tiny bones called otoliths, and as a sound sort of...

or travels through their head. Those little bones make a little noise or rattle around. Once those little bones rattle, it makes some little hairs rattle around, and that sends a signal to the fish's brain that they're hearing something. So they do have ears, but not like you and I. Our last fish question is about baby fish, and it comes from Innes, who's six and lives in Middlebury, Vermont. How are fishes born?

So fish hatch from eggs, but fish parents do things very differently. So some fish hatch from eggs inside mom or dad. For example, like seahorses, they have a little pouch. Dad has a pouch where he keeps the eggs, and once the eggs hatch inside,

He pops them out like little jelly beans. He goes through labor and pops out little baby seahorses. A lot of fish will lay eggs just out in the water, and they go floating away with the ocean currents. Some fish lay nests, and actually their mom and dad will protect the nest and wait for the eggs to hatch.

Some fish parents even carry the eggs in their mouth. They're called mouth brooders, and they will hold the eggs in their mouth until they're ready to hatch, and then will spit out all the little babies. So fish hatch from eggs, but the way that they are protected until they hatch really differs depending on what kind of fish it is. Do any fish stick with their parents after they're born, or are they all on their own?

A lot of times fish are on their own, but there are some fish, for example, cichlids, are pretty good parents. And actually the parents will take care of the little tiny fish until they're big enough to be on their own. So they will stick around and actually mom and dad sort of keep them corralled in one little area so they don't go swimming off on their own. So some fish parents are...

ones that take care of their fish after they hatch for a little while longer, while some other fish will lay their eggs and they go floating away and they never see those eggs again. In Finding Nemo, Nemo's a clownfish and his dad takes care of them. Is that true to life? A lot of times both parents will take care of a clownfish, a little one inside a menemonee, but a lot of times it's actually the moms that are bigger than the dads, which is kind of a cool thing.

Wow! We learned so much about fish today. What's your favorite thing that you learned in this episode? How they sleep, how they see, how they hear, how they take care of their babies?

If you have a question about anything, have an adult record it. You can use a smartphone. Tell us your name, first name only, where you live and how old you are. And have your adult send your question to questions at butwhykids.org.

We get so many questions, we can't answer all of them. But we do listen to everything you send, and we love to hear from you. You can always send us your feedback, what you liked and didn't like about the episodes, what you'd like to hear more of. And if you do like this show, we would really appreciate it if your adult could help you give us a review on Apple Podcasts or Stitcher or wherever you get this show. It helps other families find us, and that's a good thing.

But Why is produced by me, Jane Lindholm, and by Melody Beaudet at Vermont Public Radio. Our theme music is by Luke Reynolds. We'll be back in two weeks with an all-new episode. Until then, stay curious. From PR.