Shark Shapes Are Significant

Different sharks have different shapes. Some are blimp-like, while others are slim. A study led by Dr. Adrian Gleiss from Murdoch University Center for Fish and Fisheries Research, working with scientists from American universities, assessed the body composition of 32 shark species, looking at how it affected their buoyancy control.

A paper on their research published in the Proceedings of the Royal Society tells how their environment dictates the different shapes of sharks. Those that live in cold, deep waters tend to have very large fatty livers, sometimes making up a quarter of their body mass, which adds to their buoyancy, allowing them to move ponderously through the water using little energy.

Slimmer, more hydrodynamic sharks such as commonly encountered reef sharks, blue sharks and oceanic whitetips, inhabiting shallower, warmer water, require less energy for swimming at the high speeds necessary to catch fast and agile prey, but it means they are negatively buoyant, so they must use their wing-like pectoral fins to generate lift.

What about tiger sharks? They are mainly scavengers and ambush predators, so they sacrifice hydrodynamics for the buoyancy control that comes with a big liver.