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Perfect synchronization

Pez gruñón

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Every year in the month of March, on full moon nights, the beaches in southern California turn silver due to the shimmering bodies of thousands of fish that emerge onto the sand. These are the grunts that have come out of the sea to lay the eggs that will become the future offspring, preserving the species.

As the highest tide arrives, the grunts are brought in by the waves in groups of hundreds of individuals that will wriggle on the sand. The females leisurely twist and bury their entire bodies in the sand, leaving only their heads exposed. Each male grunt selects a mate, crawls towards her, and forms a ring around her to deposit sperm at the same time the female releases her eggs. The next wave will carry the pair back to the sea, but many will be stranded, out of reach of the water, and become prey for seagulls and other predators.

If the females spawn at the precise moment and location of sperm arrival, the fertilized eggs will remain in the moist sand for the following two weeks, beyond the reach of any marine predator, until the gravitational forces of the moon and sun combine to produce the highest tide of the month. The vibrations from the waves will contribute to the hatching of the eggs. The offspring will make great efforts to emerge from their burial, and then the water will carry the young grunts into the sea, where they will remain for the rest of their lives.

It is likely that the current grunts have inherited this spawning practice from generations that came before them, but the reason why they adopted and continue to practice it remains a mystery to researchers of animal behavior. Perhaps in the early history of grunts, there were few predators along the coast, making it safer than the ocean floor. If that were the case, it could explain why a fish would take the risk of laying its eggs in the sand, far from the safety provided by the sea.

“You cannot defend what you do not love, and you cannot love what you do not know.”