When was the last time you ate tuna? Today? This week? Maybe within the last month? For many people, tuna is a stable part of the diet because they are a good source of protein and important nutrients such as Omega-3 oils and vitamin B12. But have you ever wondered what tuna eat?
In this article, we learn more about these fish whose torpedo-shaped bodies and strong swimming muscles make them fast and powerful predators. We also find out what is the biggest threat to tuna and if they can hurt a human.
Facts About Tuna
Tuna are found in both tropical and temperate waters because they are warm-blooded fish. Unusually for fish, they are as comfortable in the cooler coastal waters of Iceland as they are in the tropical waters of Mexico. This is because they can maintain their body temperature when traveling between different temperature waters after their prey.
Tunas have two dorsal fins on their back and they can flatten one of them to reduce resistance in the water. Their tails are shaped like the crescent moon.
Tuna fish are powerful swimmers
Tuna has strong muscles which allow them to swim great distances. For example, scientists have discovered that bluefins can swim from North America to Europe and back several times a year.
Many tuna species can also travel vertically. The bigeye tuna can descend about 1,500 feet in the morning for cooler waters and return to warmer waters nearer the surface in the evening. A bluefin can move 8,000 meters down through the water in search of its prey.
How many species of tuna are there?
Did you know that there are many varieties of tuna? Some of the smaller tuna only grow up to a few pounds. The biggest tuna species, which include the Atlantic bluefin and the Bigeye, can weigh over 500 lbs and grow to ten feet long.
There are fifteen main species of tuna with some subspecies. The different tuna species are:
- Albacore tuna: found in the Pacific Ocean from British Columbia in the north to California in the south.
- Atlantic bluefin tuna: can weigh over 1,000 pounds and are at serious risk from overfishing.
- Bigeye tuna: what sets them apart is their large eyes, which is how they got their name.
- Blackfin tuna: grows to about 3 feet long and weighs 45 pounds on average and is found in the Atlantic Ocean.
- Black skipjack tuna: prefers coastal waters and can be identified from the horizontal stripes on their back.
- Bullet tuna: these small tuna live in the Mediterranean Sea and the warmer parts of the Pacific Ocean and grow to around 20 inches.
- Frigate tuna: about 25 inches long and 3-4 pounds. They are highly migratory and can be found in most oceans.
- Little tuna: only grow to about two feet long and 30 pounds in weight. Their habitat is the Pacific and Atlantic Oceans.
- Longtail tuna: found in the Indian and Pacific Oceans. At the risk of becoming endangered because they have a slow reproduction rate.
- Mackerel tuna: despite the name, they are part of the tuna family and not a type of mackerel.
- Pacific bluefin tuna: often called the king of tuna. Can weigh up to 1,000 pounds and grow up to ten feet long.
- Skipjack tuna: this species skips and jumps while swimming through the ocean, which is how they got their name.
- Slender tuna: inhabits the oceans in the Southern Hemisphere. They grow to 3 feet and 25 pounds on average.
- Southern bluefin tuna: these are highly priced and consequently overfished. They can grow up to 600 pounds and 8 feet.
- Yellowfin tuna: easily distinguished from its yellow fins. They live mainly in the Pacific Ocean, but can also be found in the Atlantic Ocean.
If you are interested in learning more about the different species, you can find out more here.
What do tuna eat?
Tuna fish are at the top of their food chain, which means they are apex predators. Most tuna eat fish, but others prefer octopus and squid. In the wild, they have a varied diet depending on what is available. They often migrate long distances in pursuit of their prey. Let’s look at some of the food in more detail.
Bluefish are an excellent source of selenium, niacin, vitamin B12, and omega-3s, and a good source of magnesium and potassium. They are migratory fish that swim in large schools and the tuna will attack these schools to feed.
Herring is a fish full of essential nutrients. It has lots of vitamin B12 and vitamin D. Also a great source of omega-3 oils. You can find herring species both in the Atlantic and Pacific Oceans.
Mackerel is a nutritious fish with high levels of essential fatty acids. They are found in temperate and tropical seas and they mostly live along the coast or offshore in the ocean environment. Here is a video of bluefin tuna feeding on mackerel.
All eels are good sources of omega-3 fatty acids. Eels also contain a good amount of calcium, magnesium, potassium, selenium, manganese, zinc, and iron. Most eel species live in the shallow ocean waters and are nocturnal.
Octopus is rich in vitamins B6 and B12 and contains good levels of omega-3 oils, phosphorus, copper, and selenium. They live in every ocean of the world in coastal marine waters. These solitary creatures spend much of their time in small holes and crevices in rocks and coral.
Jellyfish are an important source of several nutrients, including protein and minerals such as selenium and choline. They are also rich in antioxidants. You can find jellyfish in oceans all over the world. Some species prefer the surface waters while others live in deeper parts of the ocean.
These crustaceans are an abundant source of zinc, omega-3 fatty acids, choline, and lean protein among other vitamins and minerals. They are found all over the world and prefer the bottom of the ocean where they hide between rocks and weeds.
For an extended list of fish that tuna like to eat, visit A-Z Animals.
How do tuna find their food?
Tuna are known for their appetite, and they eat whenever they have a chance. They spend most of their time eating and can cover long distances just to eat. When they are not hunting, they travel two to nine miles per hour. However, when they are hunting for food, they can travel over 65 miles per hour.
All species of tuna have a keen sense of smell, which they can use to locate their prey. Some tuna, like the bluefins, also use their eyesight to find their prey. Others rely more on their noses.
What predators eat tuna?
Being such a large fish, adult tuna doesn’t have that many natural predators, except killer whales, sharks, giant squid, and a few other big fish. The biggest thread to tuna is people. For example, in the last fifty years, 74% of the eastern Atlantic and Mediterranean bluefins have disappeared, mostly because of overfishing.
Besides overfishing, the number of tuna is reduced because they can become a bycatch. This means they get caught unintentionally, often when they are still young and haven’t had a chance to breed and increase the population. Illegal fishing of the most valuable tuna species is another threat for some tuna species, especially the bluefins.
To find out more about what is being done to protect the tuna species, visit WWF.
Can tuna hurt humans?
Tuna fish are not known for attacking humans. Unlike sharks who have been known to attack people having confused them for other prey, there are no records of tuna attacking people. This is because even the largest tuna’s diet consists of smaller prey than sharks or killer whales, so there is no danger of mistaken identity leading to an attack.
However, people should only eat tuna in moderation as the mercury they contain can be harmful if consumed in large quantities. Because tuna eat smaller fish, they end up with large amounts of mercury in their tissue. Some tuna have less mercury than others. You can find out more in this article from Healthline.
Tuna is a species of fish that can thrive in all the world’s oceans thanks to their varied diet. They are not fussy eaters and will eat whatever is available to them. However, many tuna species are in danger because of human actions.
We also need to remember to only eat moderate amounts of tuna since they contain a build-up of mercury.
If you would like to ask us anything about tuna, write your questions in the comment section.