409 Dive Log Australasia December 24

A female Black Tip whaler, Carcharius limbatus , from Protea Banks using pectoral fins and its tail to create upward thrust to climb to shallow water.

When I move forward in the water, most of my energy is lost to pressure waves. Fish probably think an elephant is coming and run for cover. On the other hand, Olympic swimmers have streamlined bodies with lower water resistance. In the future, I believe Olympic champions will begin to evolve cone shaped heads, extremely wide shoulders that are even better at minimising energy loss. Other advantages will be gigantic hands and feet and light bone structure. Sharks have the perfect length to diameter ratio which minimises energy loss. Along with their incredible streamlined fusiform (conical) shape, they are designed to conserve energy.

This is important! Sharks would have to restore the energy wasted by eating more. More effort in hunting places additional strain on their lifestyles. If there is no food, they use up the energy stores in their livers. This creates further strain on their lifestyle. They may starve! The theory is that sharks which attack people are ‘Rogue’ sharks displaying abnormal behaviour. They are running low on energy reserves. Their liver has shrunk, they are starving and under stress. Healthy well fed sharks have livers up to one fifth of their body weight. They do not need to eat people.

A female Silver Tip whaler from Beqa Lagoon has made a right angle turn using pectoral fins to gain traction in the water.

DIVE LOG Australasia #409 - December ‘24 87

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