Tracking Tuna: How Do Behavior And Environment Interact?

Tracking Tuna: How Do Behavior And Environment Interact?

Grade Level



1-2 days


Life Science

Take a look at the map below. There is a colored line that shows the movement of one bluefin tuna in the ocean. What do you observe as you look at the map? What does this map tell you about the behavior of this bluefin tuna?

A map shows the topography of the sea floor in deep blues. A curving path of purple dots travels up and down the coast of California and crosses back and forth across the Pacific Ocean to a reef off of eastern Japan.
The purple dots show two years of Pacific Bluefin Tuna #66048 movement from the coast of California to the waters off of eastern Japan. Credit: Global Tagging of Pelagic Predators

This map was made when researchers attached electronic tags with sensors to the tuna. Satellites monitored their locations from space. The location data is mapped so scientists can see where the tuna travels over time. That purple line represents the journey of Bluefin Tuna #66048 over the course of two years. Scientists track dozens of tuna every year. Sound fishy? It’s not. It’s really important science!

Putting Together The Whole Picture

When researchers pair tuna location data with information about the fish’s environment, you start to understand their behavior more clearly. Below are three more maps of the same tuna swimming path. One shows the water temperatures in various parts of the ocean. The second shows primary productivity—the amount of chlorophyll in the surface waters indicates the amount of algae there. The last map shows human impacts like pollution, shipping, and fishing. Looking at these three maps, what patterns do you notice? What patterns in the swimming path and maps suggest that the tuna’s path is influenced by its environment?

A background of reds and oranges near the bottom of the graphic that transitions to yellow and white near the center, then cyan and blue near the top. A curving path of purple dots zig-zags between California and Japan, keeping mostly to areas that are white and shades of blue.
The colors show the sea surface temperature. Red is the warmest, and dark blue is the coldest. The stripe of blue near the center is missing data. Credit: Global Tagging of Pelagic Predators
The bottom of the map has large areas of purple and dark blue. The upper part of the map has areas of light blue, green, and yellow, especially along eh coastline of California. A curving path of purple dots zig-zags between California and Japan, keeping mostly to areas that are light blue, green, and yellow.
The colors show the amount of chlorophyll detected at the surface level. Chlorophyll concentration indicates areas that are capable of supporting high numbers of marine animals because they are likely productive feeding grounds. Purple and dark blues indicate low levels of chlorophyll, while green and yellow indicate higher levels. Credit: Global Tagging of Pelagic Predators
Much of the central area of the map is orange. Areas near the top and mottled with orange, yellow, and light green. A large area to the bottom right is mostly light green. A curving path of purple dots zig-zags between California and Japan. Some paths cross orange areas. One line across the ocean travels through patchy yellow and light green areas. Much of the activity along the California coast is in a light green area.
The colors show the levels of human activity with light blues and greens with a low impact and yellow, oranges, and red with an increasing impact. Credit: Global Tagging of Pelagic Predators

When science journalist Karen Pinchin stopped by Science Friday, she shared how important tracking bluefin tuna has been to understanding their behavior. A better understanding of how these fish move through the oceans and where they breed has led to changes in international fishing policy. Now, after years of steep decline, the bluefin tuna population is on the rise.

“[O]ver decades of dedicated tagging and tracking these fish from the air and watching catch landings and analyzing the otoliths, the tiny little ear bones, scientists are starting to understand… We needed systems that said, where are these fish? How many of them are we catching?” – Karen Pinchin

Related Segment

A Tuna’s Reel Life Adventures

Try Tracking Your Movements

Do you think your environment might affect your behavior?

You don’t have to be a scientist with fancy equipment to map an animal’s movements. All you need is a notebook, a pencil, and a clock. You’re going to track the movement of a very interesting mammal carefully—you!

Here’s what to do.

  1. Start your data log when you wake up. Write down the time and where you are. For example, “8:00 am, bedroom.”
  2. Every hour add your location at that time to your log.**
  3. Continue collecting data until bedtime.
  4. The next day, draw a simple map of your house (or school or town). It doesn’t have to be perfect or to scale. Label each room.
  5. On your map, make a dot for each place you logged in your notebook. Write the time over the dot or number the dots in order.
  6. Now comes the fun part! Draw a line that tracks your movement from the first dot to the next and next, and so on, until you have traced your entire day of movements on your map.

** If you want a tougher challenge, add the time and place to your log every single time you move to a new room.

Take a look at your map.

  • What do you notice about where and how you move around you home?
  • Are there any trends in your behavior?
  • How can you use this information to improve your life and your environment?

Have friends or family map their movements, too. How are your movements like those of others? How are they different?

There Once Was A Fish Named Amelia

First tagged in 2004, one Atlantic bluefin tuna was nicknamed Amelia, after Amelia Earhart, the first woman to fly alone across the Atlantic Ocean. That’s because Amelia (the fish) crossed the ocean as well. Over the course of 14 years, Amelia challenged what scientists thought they knew about her species.

At the time, many scientists and policymakers thought bluefin tuna mostly stayed near their coastal spawning areas. That assumption formed the basis of international treaties about fishing tuna, but Amelia showed that assumption was incorrect. Soon more and more data was collected about other tuna doing the same thing.

Eventually, the laws around fishing bluefin tuna changed. The information collected by scientists using electronic tags sending tracking data into space gave conservationists the evidence they needed to argue for lowering the number of bluefin tuna that could be caught for food. As a result, a fish species that was endangered is now making a comeback.

Bluefin tuna isn’t the only species that scientists are watching. For example, using the interactive maps on the Global Tagging of Pelagic Predators Program (GTOPP) website, you can explore international efforts to track sharks, seals, turtles, seabirds, and fish. It’s hoped that by combining data about many animals, scientists will gain deeper insights into how ocean ecosystems work and a greater understanding of planet Earth.

What animals would you track if you could? What would you want to learn?

A very large grey iridescent fish lays on a bue tarp placed on the wooden deck of a boat. Its eyes are covered by a green towel. A woman in yellow waders and a purple shirt uses medical tools to insert a thin probe into the flesh of the fish near its anal fin.
Dr. Barbara Block tagging an Atlantic bluefin tuna. Credit: Wayne Whippen for Tag A Giant

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Lesson by Sandy Roberts
Copyediting by Ariel Zych
Digital Production by Sandy Roberts

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About Sandy Roberts

Sandy Roberts is Science Friday’s Education Program Manager, where she creates learning resources and experiences to advance STEM equity in all learning environments. Lately, she’s been playing with origami circuits and trying to perfect a gluten-free sourdough recipe.

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