Will a shark really die if it stops swimming?

It is a common belief that if sharks stop swimming, they will die. But is this really true?

Let's take a look.

If you look at nurse sharks and tiger sharks, this belief has been proven wrong: these sharks and some other shark species can stop swimming at any time. They breathe via buccal pumps, actively "sucking" water in by using their cheek muscles to draw water into their mouths and over their gills. This causes the shark to stop moving but continue to breathe. They can rest on the seafloor without worry and can even partially bury themselves in the sand, using breathing holes behind their eyes (called spiracles) to suck water out of their gills when their mouths are covered.

But some shark species don't have the ability to suck milk with their cheeks. For example, great white, whale, and mako sharks have no buccinators at all. Instead, these sharks rely on forced ram ventilation, a breathing method that requires the shark to swim with its mouth open. The faster they swim, the more water passes through their gills. If they stop swimming, they stop receiving oxygen. They either move or die.

Other shark species, such as reef sharks, use a combination of oral pumping and forced ram ventilation to breathe. When swimming slowly, they can use a buccal pump to supplement the amount of oxygen they receive from ventilation. If they choose to stop moving for a few minutes, they do not risk their lives, although they are generally not as good at staying still as sharks that only breathe through their cheeks.

Of these three modes of breathing in sharks, the combination of oral pumping and forced ram ventilation is by far the most common. Therefore, most species of sharks do not die even if they stop swimming.

So why do many people think they do?

Sharks are often compared to bony fish, a group of fish that breathe through forced ram ventilation. Since all bony fish are frequent swimmers, many people assume that all sharks are too. Even someone without this connection might ask, “Have you ever seen a sleeping fish?”

Before we leave, one more myth needs to be busted: All fish except sharks will die if they stop swimming. In fact, the breathing patterns of non-shark fish are as diverse as those of shark species. Some fish sleep on the ocean floor like some sharks. Maybe those who think otherwise simply haven't looked at those fish before bed.

animal tags： shark