Every full moon there are fish orgies on Californian beaches.

Reading time: 2 minutes – filmed by BBC

During the full and new moons, we can witness an exceptional natural spectacle in California: unlike most fish, a species called grunion breeds on land, on the beaches of the Pacific Ocean, making a fair amount of noise. Their conception always coincides with the full and new moons because they need the tide to get to the beach.

The ritual looks like this: female fish swim as close to the shore as possible and bury themselves in the sand. They then move their tails to dig a hole in which they lay their eggs. The males follow them and fertilize. The eggs remain there until the next tide washes them away and they hatch.

Their survival was in jeopardy

During the grunions’ mating ritual, volunteer citizen scientists called “Grunion greetings” (which can be translated as “welcoming grunions”). They support Karen Martin, a researcher at Pepperdine University in Malibu, who wants to better understand the unique behavior of these fish. To date, more than 5,000 people have already provided assistance.

If the volunteers had not reported their sightings to Martin, the search for him would have been impossible, since traditional observation and counting methods do not work with grunions: they are too smart to be caught with nets or hooks.

Despite the dedication of the volunteers, there is still no exact data on the number of grunions. For this reason, they do not have protected status, although, according to Martin, they are certainly endangered. Beach erosion, light pollution, and coastal development put fish in existential danger, as do overfishing and habitat destruction. Moreover, many people collect this fish to eat it.

But the grunions have amassed a veritable army of defenders, as Martin told the BBC: “People are very sensitive to the protection of grunions. Some of them even approach people who are disturbing the fish or catching too many fish and explain to them that it is important to follow the rules.”