Every spring on California's beaches, thousands of tiny fish come ashore to spawn. As beach habitats decline, volunteer "grunion greeters" are teaming up to study and protect the tiny fish.

© 2011 National Geographic; Video courtesy Karen Martin, Michael Murrie, Beach Ecology Coalition

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UNEDITED TRANSCRIPT

During the day, southern California beaches are populated with people seeking fun in the sun.

But at night, just shortly after a full moon, when most of the people are away, these beaches are populated with small fish, coming to frolic… but in a different way.

The fish is the California grunion, and they come to the beach to spawn.

Every spring and summer, they flock to Pacific beaches, mostly from Punta Abreojos Mexico, to Santa Barbara, California.

SOUNDBITE: Karen Martin, biologist, Pepperdine University: “The grunion are sort of poster children for the beaches. It’s an animal everybody knows about, at least here in California. And they’re an animal that people really like. Here’s an animal that kind of does what we do: go to the beach to have a good time. Just like we do.”

Someone seeing this scene might think it’s a mass stranding, but National Geographic grantee and Pepperdine University biologist Karen Martin says it’s all according to plan.

SOUNDBITE: Karen Martin, biologist, Pepperdine University:“It’s a very interesting fish from a biological standpoint. It has some really unique features. The fact that it comes fully out of the water to spawn on the beach is really unusual. There are other fish that spawn on beaches, but none to the complete extent that the grunion do.”

The female begins the process by digging into the sand to deposit her eggs. The male wraps himself around the female, and, bodies entwined, fertilizes the eggs.

After spawning, most of the adult fish make it back into the ocean, leaving the eggs to develop and hatch within about two weeks.

The entire cycle is based on the tides, which are affected by the phases of the moon. Grunions make their runs when the tides are highest—at night, and during new or full moons. The lower tides that follow for the next several days, allow the eggs to develop, and the sand protects them.

And at high tide, about 9 days after spawning, the embryos are washed free before hatching.

The small grunion is near the bottom of the food chain. Far less than one percent will survive from egg to adulthood.

But humans pose the greatest threat.

Human population of the spawning seacoast has increased 700 percent since the 1920s, when the first regulations to protect the fish were created.

Catching grunion is legal during certain times of the year, but no gear or net is allowed. Only bare hands can be used.

But a large group of hunters can disrupt or even stop a run, and nearly every fish that arrives may be caught.

And beach preservation projects, such as using bulldozers and large rakes to groom the sand can be deadly to grunion nests.

SOUNDBITE: Melissa Studer, Grunion Greeter Project: "There was concern that our beach grooming practices were harming the grunion eggs incubating beneath the surface of the sand. We can successfully avoid where the eggs are and continue to do what we need to do on the beaches to keep the trash off of it”

Beach construction, such as shoreline armoring, which is placing rocks or cement walls to protect properties, can diminish or even eliminate grunion spawning grounds.

Concern for the grunion has prompted hundreds of volunteers across California to become part of the ‘Grunion Greeters’ citizen science project.