28 กันยายน

Schooling and shoaling is a kind of collective animal behaviour by fish. Any group of fish that stays together for social reasons 28 กันยายน said to be shoaling, and if the shoal is swimming in the same direction together, it is schooling.

365 About one quarter of fish shoal all their lives, and about one half of fish shoal for part of their lives. Fish get many benefits from shoaling. These include defence against predators: if fish swim in schools, it is less likely any one of them will be eaten. Also, it may help a fish find food, and a mate. The school may even swim faster than a lone fish.

Any shoal member which stands out in appearance may be targeted by predators. This may explain why fish prefer to shoal with individuals that resemble themselves. This is called the oddity effect. Some fish spend most of their time schooling. Tuna, herring and anchovy, spend all of their time shoaling or schooling, and become agitated if separated from the group. Shoaling fish can shift into a disciplined and coordinated school, then shift back to an amorphous shoal within seconds. Such shifts are triggered by changes of activity from feeding, resting, travelling or avoiding predators.

When schooling fish stop to feed, they break ranks and become shoals. Shoals are more vulnerable to predator attack. The shape a shoal or school takes depends on the type of fish and what the fish are doing. Schools that are travelling can form long thin lines, or squares or ovals or amoeboid shapes. Fast moving schools usually form a wedge shape, while shoals that are feeding tend to become circular. Schools of forage fish often accompany large predator fish. Small fish form schools, and may swim with their mouths open to filter feed on plankton.