Biology of Tunas

Why tuna keep swimming

Have you ever heard that tuna is a fish that swims all its life?
Tuna die when they stop swimming. Why?

For breathing:

Tuna breathe through their gills, but they do not have muscles to move their gills. Tuna swim with their mouths open, allowing water currents to hit their gills and draw in oxygen. This breathing method is called the ram ventilation, and many fish use this method. Therefore, if tuna stop swimming, they will not be able to take in oxygen, and in the worst case, they will suffocate to death.
For this reason, if tuna stop swimming, they cannot take in oxygen, and in the worst case, they will suffocate to death.

For keeping from sinking:

Tuna meat is extremely dense and has a high specific gravity compared to the surrounding seawater, so unless it continues to swim, it will sink. The structure of the tuna's body is similar to that of an airplane's wings, and the shape of the body generates the force that pushes it upward from below.

Many fish sleep at night, hiding behind rocks or in seaweed, and wake up when the sun is shining to begin their activities.
On the other hand, tuna continue to swim at night in order to breathe. Tuna swim at a slower speed than during the day, and their metabolism is slowed down to enable them.

Evolution to keep swimming

Tunas got the body specifically to keep swimming by the evolutiono.

Migratory fish such as tuna have red flesh.This means that they have more hemoglobin, a pigment protein found in blood, and myoglobin, a muscle pigment protein.

Red-fleshed fish need large amounts of oxygen to move their muscles, and hemoglobin and myoglobin help transport them.
Many white-fleshed fish live behind rocks or in sandy areas and do not move for very long periods of time.
Because they require less oxygen than red-fleshed fish, they have less hemoglobin and myoglobin in their blood, and as a result, their flesh appears whiter.

In other words, we can say that fish that move around a lot are red meat, and fish that do not move around a lot are white meat.

We have learned that in order to survive, tuna has changed their body mechanisms to create the characteristic of swimming for the rest of their lives.

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