Are we interrupting the kinky sex lives of fish?

Right now,

beneath a shimmering blue sea,

millions of fish are having sex.

(Cheers)

And the way they're doing it
and strategies they're using

looks nothing like what we see on land.

(Laughter)

Take parrotfish.

In this species, all fish are born female,

and they look like this.

Then later in life,

she can transition into a male
and she'll look like this.

But it's not just
a spectacular wardrobe change.

Her body can reabsorb her ovaries
and grow testes in their place.

In just a few weeks,

she'll go from making eggs
to producing sperm.

It's pretty impressive,

and in the ocean it's also pretty common.

In fact, I'll bet nearly all of you
have at some point had a seafood dish

made up of an individual
that started life as one sex

and transitioned to another.

Oysters?

Grouper?

Shrimp?

Seeing some heads nodding, yeah.

But not all fish that change sex
start as females.

Those clownfish we know
from "Finding Nemo"?

They're all born male.

So in the real world,

when Nemo's mother died,

Nemo's dad Marlin would
have transitioned into Marlene

(Laughter)

and Nemo would have likely mated
with his father turned mother.

(Laughter)

You can see -- (Laughter)

Yeah.

You can see why Pixar

took a little creative license
with the plot line, right?

(Laughter)

So sex change in the ocean
can happen in either direction

and sometimes even back and forth,

and that's just one of the many
amazing strategies animals use

to reproduce in the ocean.

And trust me when I say

it's one of the least surprising.

Sex in the sea is fascinating,

and it's also really important,

and not just to nerdy
marine biologists like me

who are obsessed with understanding
these salty affairs.

It matters for all of us.

Today, we depend on wild caught fish

to help feed over two billion people

on the planet.

We need millions of oysters and corals
to build the giant reefs

that protect our shorelines
from rising seas and storms.

We depend on medicines that are found
in marine animals to fight cancer

and other diseases.

And for many of us,

the diversity and beauty of the oceans
is where we turn for recreation

and relaxation and our cultural heritage.

In order for us to continue
to benefit from the abundance

that ocean life provides,

the fish and coral and shrimp of today

have to be able to make fish
and shrimp and coral for tomorrow.

To do that, they have to have
lots and lots of sex.

And until recently,

we really didn't know how sex
happened in the sea.

It's pretty hard to study.

But thanks to new science and technology,

we now know so much more
than even just a few years ago,

and these new discoveries
are showing two things.

First, sex in the sea is really funky.

Second, our actions are wreaking havoc
on the sex lives of everything

from shrimp to salmon.

I know. It can be hard to believe.

So today, I'm going to share a few details
about how animals do it in the deep,

how we may be interrupting
these intimate affairs,

and what we can do to change that.

So, remember those sex-changing fish?

In many places in the world,

we have fishing rules that set
a minimum catch size.

Fishers are not allowed
to target tiny fish.

This allows baby fish to grow
and reproduce before they're caught.

That's a good thing.

So fishers go after the biggest fish.

But in parrotfish, for example,
or any sex changer,

targeting the biggest fish means
that they're taking out all the males.

That makes it hard for a female fish

to find a mate

or it forces her to change sex sooner

at a smaller size.

Both of these things can result
in fewer fish babies in the future.

In order for us to properly care
for these species,

we have to know if they change sex,

how, and when.

Only