These Fish Are All About Sex on the BeachDeep Look

This baby fish is stuck. Its 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 adults-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 youre literally a fish
out of water. When they meet up, the males wrap themselves
around the females and fertilize the eggs.

Its a real scene... Then, when theyre done, they catch a wave
back home. This whole awkward affair is risky for the
parents - and for the eggs. Up on the beach, theyre 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 thats good because theyre going
to be on the beach for a while. But thats 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 cant
hatch any old time.

If they did, theyd 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
waves. The cold seawater jostles them, telling them
its time to hatch.

But the grunion 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!.