Protection
The school’s rapid changes of direction can also make it harder to track one individual: this is the confusion effect.
Searching for food
When a food source is discovered, the behaviour of the first fish can provide information to other group members.
Reproduction
These shapes are therefore not necessarily permanent: the group can reorganise quickly.
During an attack, this collective movement can make it harder for a predator to track an individual.
This formation can be observed particularly in social fish such as sardines or herring.
The fish then form a dense mass called a ball. Grouping changes how the predator can attack the school, although individuals on the edge remain particularly exposed.
This arrangement allows the group to cover a large area and may be used when travelling or searching for food.
The article particularly associates this arrangement with searching for and catching small prey.
They also have a lateral line, a sensory system able to detect water movements and mechanical changes produced around them.
This information allows each fish to adjust its movement quickly.
Attraction: staying close enough to others to maintain group cohesion.
Alignment: adjusting direction to match neighbouring fish.
Repulsion: keeping a minimum distance to avoid collisions.
Combining these three behaviours produces complex collective movements without one fish necessarily directing the whole school.
The lateral line plays a particularly important role in sensing water movements produced by nearby fish.
A reaction can thus spread quickly from one individual to its neighbours.
Each fish can change its path according to its neighbours. If a few individuals suddenly change direction after detecting danger, their neighbours react, followed by those neighbours’ neighbours.
Information can thus spread quickly through the whole group.
This is an example of self-organised collective behaviour.
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Question 1 out of 3Score: 0
How do fish manage to swim together without colliding?
What advantages can a school offer fish? (More than one answer)
What happens when danger appears?
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Conclusion
Group life can bring advantages for protection, feeding and reproduction. Through their senses and a few simple behavioural rules, fish can produce complex collective movements.
A school thus shows how simple individual behaviours can give rise to highly elaborate collective organisation.
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