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A wall of fish


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A fundamental principle of defense for animals that suffer from predator persecution is to know how to hide and go unnoticed to avoid being hunted. Many animals employ camouflage, color changes, and even mimicry with their surroundings. But how can a zebra hide in the African savannah?

Groupings, herds, or shoals are methods widely used by a wide range of animals. The method consists of hiding within a group of conspecifics. Considering that predators, when initiating an attack, need to “lock onto a prey,” which means directing their attack towards a single individual, it is obvious that it is very difficult to avoid confusion when all individuals in a group are so similar in shape, color, and size, especially when they move in synchrony. In this way, for example, when a shark spots a shoal of fish, it encounters a compact wall of fish swimming so closely together that no light enters the interior of the shoal (see photo). However, when it launches an attack, the group moves with such precision that it forms a perfect hole through which the frustrated hunter passes without having been able to capture prey.

These groupings behave like a superorganism, distributing themselves in an area for feeding and grouping together to avoid being eaten. The unity of individuals, in addition to favoring defense, is an advantage in terms of reproduction and food detection. Greater reproduction results in more individuals. Predators will settle for the sick, old, or less fit specimens. The only problem this poses for the species is human presence, as fish shoals are advantageous for fishermen with nets who benefit from this grouping.

Encountering a moving shoal underwater is an explosion of incredible beauty. It seems as if the fish move in response to an invisible and mysterious command that leads them to turn, separate, and come together simultaneously, in perfect and sublime synchrony, dancing harmoniously in an enchanted blue sea.

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