Why Fish Swim in Schools:
The Science of Saving Energy
Why do scientists think fish swim in schools?
What tool did scientists use to measure how much energy the fish used?
How much energy did schooling fish save compared to fish swimming alone?
What is a vortex, and how does it help fish?
What is “vortex phase matching”?
Why did scientists build robot fish?
What did the robot fish experiments show?
How did scientists use computers to study fish?
What might robot fish be used for in the future?
How does this research connect to climate change?
Dancing in the Water
If you’ve ever seen a group of fish swimming together, you may have noticed how they seem to move as one. They turn at the same time, speed up together, and look like they’re performing a dance.
But there’s no leader or coach telling them what to do. Each fish is deciding where to go on its own. Scientists have long wondered why fish do this.
One answer might be energy. Swimming in schools helps fish save a lot of it.
Testing Fish in the Lab
Scientists at Harvard University studied a fish called the giant danio.
These fish love to swim. The researchers placed them in a special tank shaped like a racetrack. Sometimes they added only one fish, and other times they added eight. They made the water move so the fish had to swim in place, kind of like running on a treadmill.
To measure how much energy each fish used, the scientists used a device called a respirometer. This machine tracked how much oxygen the fish used while swimming.
Just like people need more oxygen when they run, fish use more when they swim hard. The less oxygen they need, the less energy they’re using.
Fish in Groups Use Less Energy
The scientists discovered something amazing. Fish that swam in a group used less than half the energy of fish swimming alone.
Not only that, but when the fish had to swim hard—like during a sprint—they recovered faster if they were swimming in a group. That means schooling helps fish “catch their breath” more quickly.
This helps fish in many ways. Younger fish can use that saved energy to grow. Adult fish can use it to find food, escape predators, or have babies.
How Does It Work?
It’s still a bit of a mystery how schooling saves energy.
One idea is that when fish flap their tails, they create little spirals or whirlpools in the water, called vortices. These spinning areas of water push other fish forward, making swimming easier. Some scientists think that fish in the middle or back of a school get a boost from the tail movements of the fish in front.
But in a big school, it’s tricky. There are fish swimming to the left, right, above, below, in front, and behind. That means there are spinning vortices everywhere. It’s very hard to know exactly how all these water movements affect each fish. Scientists are still studying this.
Robot Fish Help Out
Because it’s hard to measure energy use in real fish while they swim in the wild, scientists made robot fish.
These “robofish” are about 18 inches long and covered in waterproof skin. They swim using motors and copy the movement of real fish. Scientists used them to test how swimming in pairs compared to swimming alone.
After over 10,000 tests, they found that the robot fish used less energy when swimming behind another robot. This was because they matched their tail beats to the water spirals left behind by the fish in front. The closer they swam, the better the match, and the more energy they saved.
Do Real Fish Do the Same Thing?
To find out if real fish act like the robots, scientists watched pairs of goldfish swimming together. Even though the goldfish changed positions often, they still seemed to match the tail movements of the fish nearby.
They were using a behavior called vortex phase matching. This means they timed their movements to use the spinning water around them.
Interestingly, the fish didn’t need to see or sense the movement of their neighbors to do this. That means they were using other clues, maybe from how the water felt on their bodies. This allows them to save energy while also staying alert for danger or food.
Computer Fish Simulations
At a lab in Switzerland, scientists used a supercomputer to make a very detailed fish simulation. This digital test let them study how swimming in schools works in 3D (three dimensions), not just flat pictures.
The computer used a learning method called reinforcement learning, which is like a video game: fish earned points for swimming well.
The computer-trained fish learned to swim into the spinning vortices of the fish in front of them instead of avoiding them. They didn’t swim directly behind, but a little off to the side. In this position, they caught the spinning water with their heads and moved it along their bodies, helping them swim with less effort.
Saving Energy for the Future
This research doesn’t just help us understand fish.
It might help us build better underwater robots that save energy and move like real fish. These robots could help count fish populations, look for pollution, or even do search-and-rescue missions.
It also helps us think about climate change. Fish get their body heat from the water around them. As oceans get warmer, fish might have to use more energy to swim and survive. Knowing how fish use energy helps scientists predict how they will handle a changing world.
Respirometer – A tool that measures how much oxygen an animal uses.
Oxygen – A gas animals need to breathe and create energy.
Vortex – A spinning movement in water or air.
Energy – The power needed to move or do work.
Robot fish – A machine that moves like a fish to help scientists study swimming.
Hydrodynamic – Related to how water moves around objects.
Simulation – A computer model that copies something real.
Reinforcement learning – A computer learning method that gives rewards for good decisions.
Predators – Animals that hunt and eat other animals.
Climate change – Long-term changes in Earth’s temperature and weather patterns.
► COMPREHENSION QUESTIONS
— please answer with complete sentences
Why do scientists think fish swim in schools?
What tool did scientists use to measure how much energy the fish used?
How much energy did schooling fish save compared to fish swimming alone?
What is a vortex, and how does it help fish?
What is “vortex phase matching”?
Why did scientists build robot fish?
What did the robot fish experiments show?
How did scientists use computers to study fish?
What might robot fish be used for in the future?
How does this research connect to climate change?
► From EITHER/OR ► BOTH/AND
► FROM Right/Wrong ► Creative Combination
THESIS — Argue the case that — for people — spending all your time in large groups is a great idea.
ANT-THESIS — Argue the case that — for people — avoiding groups and living alone is the best course.
SYN-THESIS — How might both perspectives occur — for people — at the same time?
