FOR SEA Institute of Marine Science
Back to
Tuna/Dolphin Controversy
Sample Student Lesson
The Tuna/Dolphin Controversy
Return to Main Menu

View Teacher Guide
The Tuna/Dolphin Controversy

Why would anyone get upset about a tuna sandwich? Yellowfin tuna live in warm ocean waters. These tuna often swim beneath groups of dolphins. Fishers have known this for years. No one knows why this is so. About 1960, the tuna/dolphin controversy began.

  1. Where are the yellowfin tuna often found?

What happened in 1960? The American tuna industry developed a new way of fishing. The new method depends on the mysterious relationship between dolphins and tuna. This method is called “fishing on dolphin”. This is a story about the way it works.

Dolphins are mammals. Like you, they breathe air with lungs. They must come to the surface often to breathe. Their surfacing and jumping makes them easy to spot.

  1. Why do dolphins surface so often?

Tuna fishers aboard the Joan P. spot a group of dolphins. The helicopter observer sees that tuna are with the dolphins. Speed boats are quickly lowered into the water. The motor noise panics the dolphins. They try to swim away. The speed boats encircle and “round up” the dolphins.

  1. Draw a picture to show where you think the tuna go when the speed boats “round up” the dolphins.

For unknown reasons, the tuna stay close to the dolphins. A small powerful boat called a “seine skiff&qout; moves away from the Joan P. It is towing one end of a long net. The other end is fastened to the fishing boat. The net is towed around the dolphins and tuna.

The net is a mile long. It is 600 feet deep. How long is a mile? A mile is about as long as 12 city blocks. If you were to stand on top of a 60-story tall building and hold the top of the net, the bottom of it would reach the ground.

The two boats work together to complete the circle. The top of the net is kept in place by the cork line. The bottom is held down by the heavy lead line. The purse line is pulled in. It closes the bottom of the net the way a draw string closes a purse or bag. The tuna and the dolphins are caught.

  1. The tuna / dolphins need to come to the surface often in order to breathe. (Please circle the correct answer)

Most of the net is quickly pulled aboard. A small section is left in the water. The section contains the tuna and the dolphins. The tuna move to a deep pocket of water. The pocket is near the side of the ship. The dolphins stay near the edge of the net. This is the most important time for the survival of the dolphins.

The skipper of Joan P. begins to “back down”. The ship pulls the net out from under the dolphins. Most of the dolphins swim away.

  1. Do you think it is in the tuna fishers’ best interest to safely release the dolphins? Why?

The rest of the net is hauled aboard the boat. The tuna and any remaining dolphins are caught. At any point in this fishing method, dolphins may be killed or injured. People disagree about whether it is all right to kill any dolphins while fishing. Such a disagreement is called a “controversy”. The tuna/dolphin controversy centers over whether dolphins may be killed in order to catch the yellowfin tuna.

  1. How many dolphins do you think it is reasonable to kill in order to catch the tuna? Tell why you think this.

In the past 30 years, 6,000,000 dolphins have been killed by “fishing on dolphins”. Some people want to protect the dolphins. These people are called conservationists. Conservationists say sacrifice zero dolphins. They think it is not reasonable to kill any dolphins.

Not everyone feels the same way about dolphins. For one, the government of Japan classifies dolphins as “harmful marine mammals”. Some fishers treat the dolphins as such. And when the U.S. government passed laws to limit the dolphin kill, some tuna fishers left the country. In some other countries, they could fish as they pleased. Fishers from Mexico, Venezuela, and the European Community continued to kill dolphins as they fished.

Many people felt something needed to be done. One group of conservationists urged people to boycott yellowfin tuna. Boycott means “refuse to buy”. Yellowfin tuna is sold as “light meat” tuna. The boycott tried to get tuna fishers to change the way they fish. Many people stopped buying the tuna. Some tuna fishers had trouble selling the tuna they caught.

  1. How might a boycott make fishers change?

The boycott worked. The three largest sellers of canned tuna stopped buying tuna that was caught with dolphins. All three sellers said the letters from the tuna-eating public caused them to change.

New tuna fishing methods are being developed to protect dolphins. Now 95% of all tuna are caught without harming dolphins. Other kinds of tuna, the Albacore, skipjack, and bonito, are caught on hooks. Sports fishermen catch the yellowfin tuna without a purse seine net.

Even so, about 3,000 dolphins are still killed each year. The Earth Island Institute is working to stop the practice of “dolphin fishing” for tuna. This seems like a good idea. After all, no one wants to kill dolphins.

But as with many complex issues, things may not always be what they seem. Marine Mammal Biologist, Doug DeMaster works at the National Marine Mammal Laboratory. He has spent over ten years working on this problem. He agrees that the number of dolphins killed in the past was unacceptable. But, he and other scientists believe that the 3,000 dolphins killed each year is acceptable.

  1. What do you think might make Dr. DeMaster believe as he does?

How could someone who loves dolphins think such a thing? First, he sees the dolphin population is no longer decreasing. He also sees that the U.S. tuna fleet has decreased. Plus each boat is only allowed to kill a certain number of dolphins.

This all sounds good for dolphins. The move toward “dolphin safe” tuna has been successful. True enough, but this success comes with a real threat. The threat is to the ecosystem of which the dolphin is a part. Let’s see how.

Dr. DeMaster says there are three ways people catch tuna in warm Pacific Ocean waters. “Dolphin fishing” is the way we’ve been looking at. “School fishing” is a second way. In this, tuna are surrounded in a way which harms few dolphins. The third way to catch tuna is called “log fishing”. In this, the net surrounds all of the animals that gather near floating objects. Turtles, sharks, and other animals are caught along with the tuna.

  1. a.  Think about these three ways to fish for tuna? Which do you think is most harmful to dolphins? Please explain your choice.

    b.  Which do you think is most harmful to the overall life of the sea? Please explain your choice.

Each of these three ways of fishing kills animals other than tuna. The other animals killed are called “by-catch”. The by-catch for dolphin fishing is 100 pounds of animals each time the net is set. All 100 pounds are dolphin. The by-catch for school fishing is 5,000 pounds each set. For log fishing the by-catch is 20,000 pounds each set. These by-catches consist of shark, turtles, small tunas, etc.

  1. Which fishing method is most harmful to the overall life of the sea?

This is why Dr. DeMaster is worried. He thinks a successful tuna boycott will increase “school” or “log” fishing. This could be a disaster for the life of the warm Pacific Ocean. The loss would be 50,000,000 to 200,000,000 pounds of marine animals each year. 3,000 dolphins per year would be saved.

  1. Our actions have very real consequences. Sometimes the choices are hard. Do you think the trade of 50,000,000 to 200,000,000 pounds of other marine animals for 3,000 dolphins is a good one? Please explain your choice.

Our study of the oceans shows us that each animal and plant has a special role to play. We would do well to apply that knowledge to complex problems. From the tuna/dolphin controversy we can see simple solutions to complex problems sometimes become problems of their own.

  1. What types of action could you take to let others know about this complex problem?

You can help solve this problem. In the next section, you will find some ways.

At least some of the dolphins are not waiting for people to solve the problem. These dolphins allow themselves to be “rounded up”. They are herded into an ideal position for capture. But as soon as the net is set out in the water things change. The dolphins scatter in all directions. They take the tuna with them.

The tuna/dolphin controversy is a difficult problem. Hopefully, fishers and conservationists will reach a good solution quickly. Whatever the final solution, both fishers and non-fishers need dolphins and tuna.

  1. Create a new fishing method. It should protect the dolphins but still allow fishers to catch many yellowfin tuna. Write about and draw a picture of your new tuna fishing method. (Note: The fisher’s goal is to catch as many fish as possible and as quickly as possible. The fisher’s other goal is to protect the dolphin.)

View Teacher Guide