Great hammerhead sharks swim on their sides to reduce energy expenditure

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Credit: NIPR

Dr. Yuuki Watanabe, an associate professor at the National Institute of Polar Research, Japan, and his international colleagues discovered that great hammerhead sharks (Sphyrna mokarran) swim on their sides at roll angles of approximately 60°. The sharks, which were fitted with multi-sensor electronic tags, alternated between rolling to the left and right sides every 5-10 min. However, it was unknown why they exhibit such a strange swimming style. To find out, the team built a morphologically accurate model of a hammerhead shark and conducted a series of fluid dynamic experiments. They found that when the sharks rolled, their unusually long dorsal fins effectively produced lift forces, much like airplane wings do, allowing them to avoid sinking and continue swimming at minimum energy expenditure. Thus, great hammerhead sharks have developed a unique morphology and swimming style to reduce the energetic costs of swimming.

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