The first report of a gray shark resting under a reef shelf in the Seychelles changes our knowledge of how they breathe (they don’t need to keep swimming to stay alive), and the science of sleeping sharks. The basis for this has been clarified again.

A predator in perpetual motion. I can’t sleep in our ocean. If you have this impression of sharks, you’re not alone. There’s a good reason for that. Sharks have to swim to breathe (that’s what we were told). The science of shark sleep and breathing is related, and all sharks use gills for breathing, but he has two ways to move oxygen-rich seawater over the gills.

Some sharks, called obligatory rams, “ram” oxygen-rich seawater over their gills, which requires them to keep moving.other seedThey actively pump seawater over their gills while at rest, called buccal pumps.

Evidence of shark rest: A new perspective

Today’s science shows that sharks may be stationary, and there are also suggestions that sharks are asleep. However, there is no solid evidence regarding the sleep behavior of Ram ventilators. Scientists hypothesize that they may not be sleeping at all, sleeping using half their brains (like sperm whales and bottlenose dolphins), or sleeping against ocean currents. There is.

New paper “Just keep swimming? Observation of resting behavior of gray reef sharks Medicaginus Ambryrrhinchus (Bleeker, 1856),” published this month. Fish Biology Journal This overturns our knowledge of one mandatory ram ventilator. The gray shark is an endangered reef-dwelling shark of the family Ceridae, and was a typical representative of sharks that move for breathing.

First evidence of a gray reef shark resting under a reef shelf in the Seychelles. Credit: Photography by Craig Foster | © Save Our Seeds Foundation

“During a routine research dive around Daros, we discovered a gray shark resting under a reef shelf,” said the head of research at the Save Our Seas Daros Research Center (SOSF-DRC) in the Seychelles. Dr. Robert Block begins speaking. “This is not something we believed they were capable of. Gray sharks have been thought of as a ram-breathing species that cannot rest, so when we find these sharks resting, It turns our basic understanding of them upside down.”

Stationary sharks: a surprising discovery

Researchers encountered gray sharks resting alone or in groups at various locations around the Seychelles. And all the while, the sharks seemed oblivious to the observer’s presence. This is an important observation. Scientists believe that increased arousal threshold is a characteristic of sleep, not just rest.

The sharks remained stationary except for mandibular movements, suggesting that these ram-ventilating sharks switch to buccal pumping behavior. Since there is little current at the site and the shark rests facing on all sides, the idea that resting facing the current is the only way to do so is because there is little water for gray reef sharks.

Craig Foster, founder of the SeaChange project, is one of the divers and an author of the paper. “There’s something special about tiptoeing around 25 meters underwater, staring into the open eyes of a sleeping shark, and moving carefully so as not to wake the peaceful, beautiful shark.” he says.

Implications and future research

“I love anything that challenges our current thinking, and I’ve always thought the gray reef shark is a clear example of a species that needs to swim to breathe. Obviously with this discovery. Dr James Lea, CEO of the Save Our Seas Foundation, is enthusiastic about the implications of this paper. “This raises all sorts of other questions,” he says. “How are they coping? For how long? How often? We still have a lot to learn, and that’s very exciting to me.”

If gray reef sharks can switch up their breathing and rest, we may be able to learn more about similar sharks. “It’s important to understand how they use their environment and how it changes in response to changing environmental conditions,” explains Dr. Lee. “How important is this rest, or even the possibility of sleep, for sharks? And how will they be affected if they are unable to rest if conditions change, such as rising or falling oxygen levels due to climate change? Will I receive it?”

remind us of our connection to nature

The authors all agree that this discovery also tells us a lot about ourselves and our relationship with the natural world. “I hope these discoveries remind us how much we still don’t know and how interesting that is. Science can get quite a lot wrong. That’s a lot, and that’s okay,” Dr. Block recalled. Foster believes what we know about the wild is critical to conservation. “Knowing how our shark family sleeps brings us closer to their fascinating world, and awakens us from our own slumber to remind us that we cannot live without these amazing marine creatures.” ,” he said.

Reference: “Just keep swimming? Observation of resting behavior of gray reef sharks Medicaginus Ambryrrhinchus (Bleeker, 1856)” by Robert W. Block, Craig Foster, and James S.E. Lee, November 20, 2023, Fish Biology Journal.
DOI: 10.1111/jfb.15623