The three rules of schooling: Avoid collisions with your neighbours, remain close to your neighbours, and move in the same direction as your neighbour
Text by Scuba Diver Ocean Planet
Image from Shutterstock
It’s a hypnotic, awe-inspiring sight – thousands of fish moving in sync, as if with one mind. Schooling fish is a phenomenon that arises from something known as “swarm intelligence”, in which independent units spontaneously form organised structures or patterns. But how exactly does it work? The process is far simpler than you might imagine.
1. THE BENEFITS OF LEADERLESS GOVERNANCE
It’s a form of aquatic anarchy – in a school of fish there is no single leader, no one individual controlling or determining the direction or structure of the collective. In a school, decisions are made according to the collective behaviour of self-organised systems. Self-organisation is when structures appear at the global level of a system as a result of the interactions of its lower level components (Bonabeau et al., Swarm Intelligence, 1999); these patterns on the global level emerge as intelligent ones, but are probably unknown to each individual agent.
It has been found that each fish is only responding to the behaviour of its nearest neighbour at any one time. Research published in the journal Proceedings of the National Academy of Sciences shows that fish coordinate their movements according to a simple set of rules, using mainly visual clues, and adjusting their position based on that of their neighbours.
According to the lead researcher, James Herbert-Read of Sydney University’s school of biological sciences, the rules include accelerating towards neighbours that are far away and decelerating when neighbours are right in front. They also found that a fish only responds to a single nearest neighbour at any one time.
So, when any fish finds itself close to a predator, it naturally moves away from it, its neighbours then follow suit, and the information is passed, fish to fish, between the whole school.
2. WHY FISH SHOULD STAY IN SCHOOL
Not only does swimming with the crowd minimise the chances of an individual being picked off by a predator, but a study published in the journal Current Zoology suggests that hundreds or thousands of creatures moving in sync also has a physical impact on the environment, generating waves of sound and pressure, and that these vibrations are thought to confuse the senses of predators, specifically affecting their lateral line receptors, electrosensory perception and auditory ability.
3. SCHOOLING BY NATURE
Schooling has also been shown to be a genetic predisposition, rather than learned behaviour; it makes sense that fish would evolve to swim together to better protect themselves from predators. Research also shows that most fish species will school at some point in their life cycle,
The gene identified for the schooling instinct is connected to the gene for the lateral line – a strip of sense organs along the side of the fish’s body that picks up vibrations in the water much like the tiny hairs in our ears pick up vibrations and interpret them as sound. Interestingly though, fish navigate and school based on visual information, with the information they receive through their lateral line playing a secondary role.
BONUS FACT: DID YOU KNOW…
Schooling and shoaling are technically very different behaviours. Fish that are loosely swimming together, all following the general direction, but maybe foraging and feeding, are said to be shoaling. But schooling fish swim in synchronised patterns in tight formations, often as a means of defence.
To find out about more fascinating facts about marine life and diving destinations, check out Scuba Diver Issue 4 / 2015 here.
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