Fish Schools
DB: This is Earth and Sky, with a question from a listener. He writes, “How do fish stay together in schools?”
JB: From large tuna in the ocean to tiny minnows in a pond, many species of fish swim together in groups, This is what scientists call schooling. The school might contain just a few fish, or it might have millions of members. The fish swerve and turn together in a split second. They neither collide nor scatter apart.
DB: Fish do that by using two senses to maintain the spacing in a school. Fish use their vision and another sense – that humans don’t have called the “lateral line system”. The lateral line system – sometimes called the “sense of distant touch” runs all along the sides of a fish’s body. It’s sensitive to vibrations in the water. That’s how fish can sense the direction of water movements made by tails of fish in front and next to them. It allows the fish to quickly detect changes in water pressure made by approaching rocks or seaweed – or even very low-frequency sounds. The fish then decides to speed up, slow down or change direction.
JB: As in a flock of birds, there’s no leader. The movement of the school is the sum of individual decisions. When fish are hungry and safe, the school may disperse to feed. But at the approach of a predator, stragglers quickly rejoin the group – or risk getting eaten. Thanks today to the U. S. Fish and Wildlife Service and to the National Fish and Wildlife Foundation. We’re Block and Byrd for Earth and Sky.
The following person was interviewed for today’s program. our thanks to:
Dr Julia K Parrish
Research Assistant Professor
Department of Zoology
University of Washington
Author’s Notes:
To better understand how schooling works, researchers tried to model schooling on a computer, using a set of rules based on forces of varying strength of attraction and repulsion. They were actually able to see some schooling in computer fish.
Fish are born with the ability to school. But very young fish, who are too small to swim against a current, often don’t school. Scientist think that’s because their muscle and nervous systems are not yet developed enough. As fish grow into what is roughly analogous to the teenage stage, they are more likely to school. As they get older and bigger still, and there is more competition for food, many species spend less time in a school.
Additional Teacher Resources
Craig Reynolds, Boids (Flocks, Herds, and Schools: A Distributed Behavioral Model.): Boids
This site consists of a computer model of coordinated animal motion such as bird flocks and fish schools, as well as a wealth of in-depth information into a variety of facets concerning the social and physical science behind flocks, herds and schools. This site is geared more to older students.
Harvard University, Harvard University Gazette: Scientists Show How Fish Save Energy By Swimming In Schools
This article explains how, using a tank designed to mimic a turbulent waterway, scientists have found that fish employ a unique and clever swimming motion to harness the energy of eddies in flowing water. By essentially hitching a ride and letting these vortices propel them along, the scientists say, fish can swim against a current with considerably less exertion that is required in calmer settings.
