Call it the original synchronized swimming - fish, moving smoothly and swiftly, all in coordination with hundreds of other fish - that’s how fish do school.
Sure, it’s a pretty show, but what’s with the whole production? Gathering together and moving in a school helps smaller fish protect themselves from predators, eat better and swim more efficiently.
Not all groups of fish are schools, either. Fish hanging out together in an organized group is known as shoaling - to graduate to a school, the group needs to make coordinated movements together. A school usually consists of only one type of fish as well.
For what seems to be a highly complicated dance number, it’s striking to know that there’s no leader. No pilot at the front of the flying “V” leading the way, like in Canada geese. Instead, it’s more of a domino effect. As a group of fish comes together, they react based on their neighbor’s movements. When one fish heads left, the fish next door then turns left, and so on and so on. They follow each other by watching those around them, but also by using some special fish-only skills.
To do that, fish rely on their lateral line, a feature unique to fish, which senses vibrations in the water and changes in water pressure around them.
You may have seen this behavior while fishing Iowa’s larger rivers and flood control reservoirs, where gizzard shad are native (they are not native to Iowa’s smaller constructed lakes and can have negative impacts on the fish communities in those systems). Crappies often gather together in schools, and sometimes smallmouth bass will huddle up before winter.