PBS DIGITAL STUDIOS
This baby fish is stuck.
It’s ready to hatch,
to swim out into the open sea.
So how did it get here –
stranded up on the sand?
It all started two weeks ago,
when its parents left their watery home
for an adult’s only beach party.
During the very highest tides,
California grunion ride in on the waves to
get as high up on the beach as possible.
The females start digging with their tails,
burrowing down to lay thousands of eggs under the wet sand.
The males cruise the beach,
searching for females.
Not super easy when you’re literally a fish out of water.
When they meet up,
the males wrap themselves around the females and fertilize the eggs.
It’s a real scene…
Then, when they’re done,
they catch a wave back home.
This whole awkward affair is risky for the parents and for the eggs.
Up on the beach, they’re all on their own,
completely out of their element,
but grunion eggs are tough.
The outer membrane, called a chorion,
protects them from drying out
and keeps them from getting crushed.
And that’s good,
because they’re going to be on the beach for a while.
But that’s the whole idea,
the ocean is full of predators
looking to gobble up a tasty fish egg.
Growing up in this sandy nursery gives baby grunion an advantage.
Though nowhere is truly safe.
But fish still need water,
so these eggs can’t hatch any old time.
If they did, they’d suffocate in the dry sand.
So they have to time it perfectly,
waiting for the gravitational pull of the sun and moon to line up,
creating an extra high tide, which only happens twice a month.
The baby grunion wait for the signal:
The cold seawater jostles them,
telling them it’s time to hatch.
But the grunions still have to break
out of their tough eggs before the tide recedes.
So they release special enzymes from their tail
that eat right through the chorion.
They come bursting out.
And swim for their lives,
as the waves sweep them out, into the briny deep,
where they belong.
Hey. It’s Lauren.
Looking for something to watch next?
Check out Gross Science,
also part of the PBS Digital Studios’ lineup,
where Anna shows you the more adorable side of hideous parasites
and unspeakable bodily functions.
You’ll also love NPR’s awesome science channel “Skunk Bear”!
This week, you can follow them into a cuddly colony of vampire bats.
See you next time!