A school of fish moves in the direction of food.
While swimming, the fish also breed.
The number of children and their strength depends largely on
the amount of food that is found.
The school regularly splits into parts, when food is found in different
directions.
Individual fish or parts of the school that go into a direction in which
no food is to be found will die of starvation.
Fish or parts of the school that enter polluted waters also die.