The Moon is responsible for frequent 'fish orgy' on California beaches, scientists say

Scientists are weighing in on the millions of fish flocking to Californian beaches for a sex party.

Yes, fish. You may've thought I just said spring breakers but it's millions of unruly small fish which have been causing a stir during certain times each year on Californian beaches and beaches in Baja California, Mexico too.

When

The fishes' sex-filled congregation on the beaches of the American Pacific Coast typically take place from February through to September - the most raunchy months between April to June, California Sea Grant explains.

And the event sees thousands, if not millions, of fish fling themselves onto the sandy beaches in a bid to get down and dirty.

However, rather differently to spring breakers, the fish are here with a strong purpose.

Spring breakers are no match for grunions (Luis Sinco / Los Angeles Times via Getty Images)

Why and what

The fish flock to the beaches during these set month of the year in a bid to procreate. But what actually happens?

Well, first things first, as per California Sea Grant, the frisky fish are 'hot-dog sized' fish called grunions.

The female fish are the first to come to land before 'wriggling and twisting their bodies' to make a little nest in the sand. They then lay their eggs and wait for the men to arrive.

Male grunions then spoon the female and 'secrete their milt or semen' which runs along the female's body before plopping onto the eggs and fertilizing them. The job done, the male grunions then scarper back to the sea and the female grunions follow shortly after.

Each nest can be fertilized by 'up to eight male grunions' and it only takes between '30 seconds to several minutes' for a grunion to do the deed. It's no surprise why the event has been dubbed a 'fish orgy' or if we're not being such sniggering children about it, it's also known as the Grunion Run.

But without a calendar alert to let them know when to head on over to the beaches, how do the fish know when it's time to party?

It's become known as the Grunion Run (Don Kelsen/Los Angeles Times via Getty Images)

How

The grunions are only able to get to the beach to get frisky when the tides are at their highest and for those of us who swiftly dropped physics at the first opportunity we could, the level of the tide is controlled by the moon.

Tides are their highest 'twice in the lunar cycle' and it's then when the female grunions take to the beaches to lay their eggs, so that they can position them just above the high tide line meaning they're out of the water to soak up enough oxygen for as long as possible.

Being safe on land also means they're away from any other fish which might be hunting for a snack, although, on the other hand, they're not safe from hammered spring breakers stumbling to find their own night-time fun.

However, the heat from being tucked in the sand also helps the eggs 'develop faster,' California Sea Grant notes.

Once the next high tide does come about, the eggs have had enough oxygen and warmth to develop nicely and the impact of the sea causes the embryos to hatch.

And there we have it, the birds and the bees of the grunion. The perfect interesting fact to tell whoever you're with the next time you stumble onto a California beach late at night and see thousands of fish procreating.