Will sharks drown if they stop swimming? This is one of the most common questions about sharks today. Most people believe that sharks need to keep swimming to stay alive and several pieces of literature on sharks support this. However, how true is this belief?
Will a shark drown if it stops swimming? Let me put it this way, not all sharks will drown if they stop swimming. So, the answer largely depends on the shark species in question. For example, sharks that are obligate ram ventilators will need to continuously swim to breathe. However, for buccal pumping sharks, they do not need to keep swimming to breathe. You see, a shark may or may not drown if it stops swimming depending on its method of gaseous exchange.
If your next question at this point is “the difference between ram ventilation and buccal pumping?” then, let’s proceed.
For you to understand this properly, let us see the mechanism behind gaseous exchange in sharks.
How Does Sharks Breathe?
Sharks are fish and they take in oxygen through their gills. However, the way sharks breathe may differ from other fish species such as bony fish. This is because sharks tend to have fewer muscles than bony fish around their breathing organs.
When sharks breathe, they collect oxygen from the surrounding water. They usually do this by opening their mouth and letting water flow in. Note that sharks have a nose too, however, their nose is exclusively for the smell.
The water that sharks take in flows over their gills. Here, you will find hundreds of gill filaments with each possessing thousands of lamellae. These are leaflike flaps with blood vessels.
These blood vessels absorb oxygen from the water that flows in. Then, the water collects carbon dioxide and flows out through the gill slits.
Sharks would usually get up to 80% of the oxygen present in the water. Whereby, the water contains only about 1% of oxygen compared to 21% available in the air. Hence, a shark would rather need to let water flow constantly over their gills to maintain steady oxygen flow.
Bony fish, for instance, have the capacity to actively pump water through their mouth and over their gills. Is this so with sharks? Well, sharks have less developed organs for breathing. This is why researchers thought they have to swim continuously to breathe.
How do we then account for shark species such as wobbegongs, nurse sharks, and others that rarely swim?
This is where we now differentiate between buccal pumping and ram ventilation?
What is Buccal Pumping in Sharks? And How Does It Work to Help Them Breathe?
When you see some sharks, they lie almost motionless usually on the seafloor. This doesn’t mean anything is wrong with these sharks. They are simply resting and breathing by pumping water through their mouth over their gills. This process is what we know as “Buccal Pumping”.
Buccal pumping involves sharks using their cheek (buccal) muscles to draw water into their mouth. And, this water flows over their gills. They are able to do this because of their somewhat developed buccal and face muscles.
Sharks that breathe through buccal pumping are usually inactive species. They also have a few noticeable differences in their body compared to other species.
For instance, their dorsoventral side appears flattened. And, they tend to have a more noticeable spiracle, a breathing hole that occurs behind the eyes.
The spiracle helps these shark species to draw in the water when they are in certain positions. For example, when they bury themselves in the sand and cannot draw in water through their mouth.
The water still flows over the gills for gaseous exchange.
Sharks species that can breathe through buccal pumping includes wobbegongs, angel sharks, and nurse sharks.
Historically, the ancestors of sharks’ all used buccal pumping to breathe. They didn’t have to continuously swim to breathe.
So, what happened?
What is Ram Ventilation in Sharks?
Evolution happened! Shark species evolved and became more active, hence noticing that taking in water as they swim was more energy efficient. As a result, they adapted accordingly, making the method of pumping water a secondary means of breathing.
When sharks swim, they “ram” water into their mouth, and this water flow over their gills. This method of swimming and letting the water flow over the gills is what we know as “Ram Ventilation”.
Most shark species can switch from buccal pumping to ram ventilation. This depends on what the shark is doing, that is, whether it is resting or in motion. Thus, sharks in this category can stop pumping when they start swimming and attain a speed where they can force more water in than they could through buccal pumping.
An example of sharks that can switch between the two breathing methods is the Sand Tiger shark.
Some sharks on the other hand lost the ability of buccal pumping entirely. Sharks in this category will need to continuously swim to breathe, they are called Obligate Ram Ventilators. If they eventually stop swimming, they will definitely drown.
Examples of obligate ram breathers include the great white shark, the whale shark and, the mako shark.
These sharks swim continuously in a forward motion to maintain breathing.
Are you wondering if these sharks ever rest? Or How they even cope? Let’s see how they do this.
How Do Obligate Ram Ventilators Sleep or Rest?
As a human, you would feel the stress already hearing that these sharks would need to continuously swim to breathe. However, don’t worry as these sharks aren’t like us.
With the turn of things, it appears it is more work for these sharks to stop swimming than to continue swimming. Resting to these sharks may not include standing still.
A study of the lemon shark which can switch between buccal pumping and ram ventilation shows that juveniles exhibited more efficient breathing up to 6% while swimming than when not swimming.
Even when the sharks are resting still, they face the water current to allow water flow into their mouth directly.
Keeping track of obligate ram ventilators can be very difficult. This is because they are in continuous motion. Certainly, these sharks rest, every animal does in order to recharge. However, the method is not always the same.
Scientists may not be exactly sure how and when obligate ram ventilators rest. But, a study of the spiny dogfish showed that the brain doesn’t control their swimming. Instead, it is the spinal cord that does the job.
As a result, it is possible that they are able to shut their brain while resting, meanwhile, they are still swimming.
On another note, sharks can take advantage of the environmental factors affecting the level of oxygen in the water when trying to rest. These factors can include the time of the day, water salinity, and temperature.
As a result, reef sharks which are obligate ram ventilators were found resting motionless in the “Caves of Sleeping Sharks” discovered in Isla Mujeres, Mexico in the 1970s.
The water in the caves has reduced salinity and increased oxygen. This made the scientists believe it was easier for the sharks to breathe in such conditions.
How Do Sharks Cope in Low Oxygen Environment?
When in an extremely low oxygen environment, sharks face hypoxia. This is a condition of oxygen deficiency.
In response to this condition, sharks either try to conserve their oxygen or improve the rate of oxygen intake. This depends on the sharks’ method of breathing.
Hence, when buccal pumping sharks face hypoxia, they tend to decrease their activity level in an attempt to conserve energy. Also, they focus more on increasing the force of pumping to take in more oxygen.
However, for obligate ram ventilators, they tend to increase their speed of swimming when faced with hypoxia. In addition, they open their mouth wider. They do this to increase their oxygen intake. Of course, they can’t just stop swimming to conserve energy.
This may seem to counter what you’d expect. But, just maybe that’s the best way these sharks can conserve their energy. Reference
Will Great White Sharks Drown If They Stop Swimming?
The Great White shark as listed above is an obligate ram ventilator. Certainly, these sharks need to swim continuously to breathe.
So, if a great white shark stops swimming, it will definitely drown since it can’t get oxygen without moving. This shark species among other obligate ram ventilators cannot force water into their mouth due to their poorly developed check muscles.
Therefore, to emphasize, Yes! The great white shark would drown if it stops swimming.
Will Whale Sharks Drown If They Stop Swimming?
Whale sharks are also obligate ram ventilators just like the great white shark. These sharks are migratory species.
They swim continuously with their mouth wide open to let water in. The water subsequently flows out of the gill slits after gaseous exchange within the gills.
Buccal Pumping Sharks VS Obligate Ram Ventilators
Among the over 400 shark species in the sea, it is only about 20 species that are obligate ram ventilators. The majority of the shark species can switch between buccal pumping and ram ventilation.
This implies that as much as you may think that sharks would drown if they stop swimming, it is only very few of them compared to the number of existing shark species.
Conclusion
In the end, you’ll see that sharks can actually drown if they stop swimming. However, it all depends on the shark species and the method of breathing adopted.
Summarily, buccal pumping sharks won’t drown if they stop swimming. And, on the other hand, obligate ventilate sharks would eventually drown if they stop swimming.