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Deep sea sharks are a great curiosity. While most species of sharks are known for not being buoyant and having the potential to sink if they were to stop swimming, a new study has revealed that the Bluntnose Sixgill Shark and the Prickly Shark, both deep water creatures, have what experts call “positive buoyancy”.
Researchers from the University of Hawaii and the University of Tokyo explain that these species have to swim much harder when they go down than when they go up. When they do go up, however, they can refrain from using their tail for several minutes at a time and simply glide upwards for a while.
For their study, published earlier this month, on June 10, in the journal PLOS One, the researchers relied on an accelerometer in order to record the swimming patterns that sharks exhibited up and down their habitats. They paid attention to the creatures’ speed, heading, tail beat frequency and general body orientation, and this helped them to determined whether the animals were positively buoyant, negatively buoyant or neutrally buoyant.
The results were fascinating and unexpected as no one thought they’d find sharks that are positively buoyant. Carl Meyer, study author and professor at the University of Hawaii’s Institute of Marine Biology (HIMB), gave a statement informing that the team of researchers had to felt the need to conduct two (2) different sets of experiment in order to confirm the initial observations that they hah made.
He went on to explain that “During vertical movements, all deep-sea sharks showed higher swimming efforts during descent than ascent to maintain a given swimming speed, and were able to glide uphill for extended periods (several minutes)”. What this means is that the Bluntnose Sixgill Shark and the Prickly Shark are without a doubt positively buoyant in deep sea waters, their natural habitat.
In an attempt to get a better look at these habitats, the researchers also mounted cameras on sharks before sending back into the water. Their efforts paid off as the data collected showed that sharks prefer to stay in deeper waters during the day, but that during this time they become sluggish swimmers, most likely due to the cold water cooling off the sharks’ swimming muscles.
The working theory is that positive buoyancy actually helps these marine creatures survive the harsh deep sea habitat that’s often low on food for them. Meyer believes that this trait either allows sharks to be very stealthy due to their gliding ability, which in turn helps them take other animals by surprise when hunting, or that gliding come in handy during the night time, when sharks migrate to shallower waters.
Image Source: wdfw.wa.gov
