Shoal or School
Do you know the difference between a shoal or school of fish? While in the water we see plenty of fish that group together. There are certain behaviours and characteristics to look out for to determine if the group is a shoal or school.
All social groupings of fish are considered a shoal, but only some shoals are schools.
Shoaling is when a group of fish congregate together. There is no coordination of movement between each fish, they all move and forage in their own way. Being in a shoal allows for protection from lager predators ‘safety in numbers’. Fish that group together are normally members of the same species, often in similar size and colouration. Any fish that does not blend in with the majority of the group, has more of a disadvantage of being the target to predators. This is known as the ‘oddity effect’, being the odd one out. Shoaling also allows for better foraging, more likely to find food and individuals can feed more safely than if alone.
We often see shoals of convict or eye-stripe surgeonfish feeding on algae growing on the reef.
Shoaling becomes schooling when the fishes’ movements or behaviours become synchronised. If the fish get closer to each other and are moving in the same direction at the same speed, this means they are schooling.
We have a few sites where we know we will see schooling blue lined snappers. We also often see schools of fusiliers during our diving and snorkelling excursions too.
How do fish school
Only some species of fish school. Schooling is not learnt but develops over time through instinct. The fish must develop fast response systems. Young fish often do this in pairs to practice before joining larger schools. Vision is a key sense for schooling. Most schooling fishes’ eyes are on the side of their heads, they are able to easily follow and track the fish next to them. This is also with help of particular markings on schooling fish which help indicate to each other which way the school is moving and how fast. It is also observed that after dark when the fish can no longer see each other schools often turn into shoals. Pheromones and sound also contribute to fish schooling.
Keep an eye out next time you see a group of fish and try to determine if the group is shoaling or schooling. Otherwise check out this blog go fish relationships for more!