Short Stuff: Do Fish Get Thirsty?

One of the greatest questions we’ve ever heard, answered (in a roundabout way).

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Episode Transcript

Speaker 1 (00:04):
Hey, and welcome to the Short Stuff. I'm Josh, and
there's Chuck and this is short Stuff coming at you
with a question I had never thought of until I
was on our old site how Stuff Works, and came
across an article by Nathan Chandler which asked a surprising
question that makes a lot of sense if you think
about it. Do fish which spend their lives in the

(00:25):
water ever get thirsty? It's a great question, and I
immediately thought of possibly one of my favorite, definitely one
of my favorite all time comedies, maybe my favorite, the
movie Arthur. I thought you were gonna say family Ties
movie comedies Arthur. When Arthur says I must think that

(00:45):
fish get awfully tired of eating seafood. That's one that's
not even one of the good lines. I've never seen
that one you're talking about, Arthur. Yeah, with Russell Brand.
Oh god, you know I'm mad, I am right now. Yeah,
I know you're a big Russell Brand fan. Even though
Hodgeman was in that version, I think he really was.

(01:07):
Um and uh yeah, that's my big connection to it.
That's his claim to fame. So h No, I haven't
seen Arthur, but I will just to keep this one going.
How about that? Wait, you haven't seen the original either?
For real, I've never seen any Arthur dude. It's one
of the best comedies of all time. Uh. Doesn't it
have that song between the Moon and New York City? Yeah?

(01:29):
One of the great movie theme songs of all time.
It is a good theme song. I know it's crazy,
but it's true. Um. Nice. Uh. So let's keep going though,
because we need to get back to this question. Do
fish ever get thirsty? Right? Uh? And the first thing
that Nathan Chandler points out, which is, you know, very
easy and I think Nathan interviewed some people, uh that

(01:52):
no more than we do about fish and their needs
and wants. But the first thing they point out is like,
that's kind of a weird question because you can't really
tell whether an animal like thinks I'm thirsty or not.
The real question is basically, do fish drink and do
they need to hydrate like we do? Yeah, And Nathan
Chainer is like, come on, this is what I meant
pencil neck right? Um? So uh that that is ultimately

(02:16):
the question that we're after. So um, if you are
ever thirsty, you know, there's it's kind of like hunger,
like you have a sensation that tells you you need
to eat food. We need energy. This is the same
thing your body sends you all sorts of cues and
signals that says you need to drink some water because
we need to be hydrated. And the whole point of
staying hydrated is not just to drink water, which is fun,

(02:38):
but that's not the point. The point is that we
have all sorts of like little minerals and salts and
electro lights, according to the good people at Gatorade, in
our bodies that we need to keep at a certain level,
and we keep them at a certain level of certain
concentration by regulating our water intake. Right, So that's how
we stay hydrated. And that's the point of staying hydrated.

(03:00):
And it turns out that fish basically have to do
the same thing despite living in water, or actually I
guess because they live in water. Yeah, This whole process
is called osma regulation, and fish do this. You know,
we're very closely related to fish, so it's not the

(03:20):
most different process for them. Even though we don't have gills.
It would be kind of fun if we did, but
we don't. But their kidneys are a big part of
this obviously in maintaining just like with us, those salt levels. Uh.
And then they do have those gills, and those gills
have cells that exchange water and salt, and again just
trying to keep the right uh electro political balance. Yeah,

(03:45):
I think that's a great way to put it. Or
I could just say electro light balance. Okay, I like
the electrolytical all right, so you're gonna keep it in. Well,
I mean I'm not gonna I'm not gonna cut it out.
I've said much dumber things. I don't think it's dumb
at all. I think sing and chuck. I have to
say if if that isn't a term, you're just coined
a term, because I'm going to spend the rest of

(04:05):
my day's promoting electrolytical Okay, great. So, Um, the it
turns out though, this OSMO regulation, I guess the um,
the process or the systems or the components for carrying
out OSMO regulation are the same basically across fish species.

(04:26):
You know, similar enough that you could call them the
same for our purposes today. Um. But what they do
or how they do it, or what their goal is
depends on what kind of water the fish lives in
salt water or freshwater, or if the fish can kind
of transcend both kinds of water. And I propose we
take a break and come back and talk about the
setup that I just did. Sounds great, all right, freshwater fish?

(05:20):
Should we start there? Yeah? I think so. It's a
good place to start your common large mouth bass. Let's say,
sure that can eat a squirrel during a squirrel stampede.
That's right. I forgot about that. So I learned a
couple of interesting things here. One is that freshwater fish
don't drink like actively because it's just gonna dilute their

(05:41):
blood and other fluids in their body really quickly. Um.
Obviously they're what's inside their body, their tissue and their
blood is going to be saltier than where they are
because they're in freshwater. Uh, so they would just act
as a big salt water or I guess salt sponge
if they were to drink too much. So. Uh. The

(06:02):
other thing I learned is that they urinate. They're constantly urinating, right,
that's the only way to say it. And I did
not know this. So the and the urine they pe
out is super super watery. Um, because again, they're they're
retaining and keeping ahold of as much of those salts
and minerals and electro lights that they possibly can um

(06:23):
because it's just they're not getting it from their surrounding environment,
that is the fresh water. So like you said, they
they they they are preventing from their solution in their
blood from becoming two diluted. That's the point of their
OSMO regulation. Correct, that's right for the freshies, okay. And

(06:45):
so if they do it correctly, if their cells and
their gills and their kidneys are working properly, they're streaming
out there accepting salt for the body wherever it can
get it, and they're peeing out tons and tons of
water that they're taking on and keep being the salt.
But um, if you go to a salt water like
the Sea saltwater area, you find pretty much the opposite

(07:09):
process happening for the same reason. Yes, And the cool
thing here is that saltwater fish actually drink through their mouths,
and they drink through their mouths to stay hydrated. So
they're drinking this ocean water and so the big rub
there is they have to avoid losing water too much
to that salty environment. Out there, and they also have

(07:31):
to keep from getting too salty, Like you know, they're
drinking in the saltwater and they have to keep that
excess salt out, so their kidneys are kind of not
working over time. They're doing their regular job, like they
don't know how hard they're working compared to other kidneys,
but their kidneys are removing that salt and conserving the water.
And then they have those salt cells and their gills

(07:51):
pumping salt into the water. So again you have that
same exchange going on. It's just sort of backwards or
the opposite. And you can imagine, and their urine is
super salty urine and um kind of light on the water, right,
it's super concentrated solution that they're peeing out. I would
think so, And then I said this earlier. There are
fish that can exist in both freshwater and saltwater. And

(08:14):
now that you know right now that you know about
OSMO regulation, it's like, well, wait a minute, how does
that work? And you can take the salmon as a
really good example, because when the salmon go to spawn,
they go to spawn and freshwater, usually upstream in some
river because they like to make things hard on themselves,
which means that when they come to spawn, they leave

(08:36):
their saltwater habitat and enter a freshwater habitat. Yeah, and
it was it was interesting when I was reading this,
I was kind of like, well, how in the world,
like do they have had their organs evolved to be
able to do both? And it kind of has in
a way, but not both at the same time, because
salmon are really smart. So what they do is they

(08:57):
don't go straight from their freshwater right into the saltwa water.
They hang out a little bit and what they what's
called like a staging area before they complete their migration,
and it's located in a space where they get a
little bit of the freshwater and a little bit of
the salt water and they just they just hang out
until they regulate, right. Um. And it's just it's as

(09:19):
simple as that that they use brackish water to kind
of like prep themselves for the changeover. And I would
guess they do this the opposite when they go back
into the sea again or the saltwater environment. The problem is,
like everything, there's a there's a conundrum that they're facing
thanks to climate change where um sea ice is breaking

(09:41):
up more and more traveling further and further south and
into um salmon's breeding grounds and there it's actually the
fresh water that's melting off of the sea ice is
affecting the brackish water so that the salmon have less
chance of a to to use that area as a
stage area. Yeah, it kind of just screws up their

(10:02):
staging area because they're they're used to that area being
having a certain amount of salinity, and then when you
introduce that melting sea ice, it just screws everything up.
Yet another thing that's happening. It is so chuck. How
much seawater can you ingest at a time, like me, um,

(10:23):
I don't know, three and a half percent of my
body weight, No, three and a half percent salt, I
think by weight. Like, you know, if you're trapped, We've
talked about this before, if you're like stranded out in
the ocean, you know you will die if you just
continue to drink seawater because you're gonna dehydrate, but you
can't drink a little bit of it. Yeah, I don't

(10:43):
know if we should advise anybody doing to do that though,
I don't think so. But you're you're not gonna die like,
all right, let's forget your stranded You're just on the
beach one day and you go, like, get a small
cup of ocean water and drink it. You'll be fine.
I don't think we should tell people to do that either.
Let's just stay away from the encouraging drinking seawater in general.

(11:04):
All right, how about this, You're in your house and
you take some very clean water and clean table salt
and mix it together. You could drink that and you
a little bit of that and you'd be okay. No,
I'm still not okay with that either. All right, well,
then why do you ask how much we could drink?
I just want to know how much you personally could.
Is short? Stuff out? Short stuff is out? Everybody. Stuff

(11:30):
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