409 Dive Log Australasia December 24

Epaulette sharks have tough sandpapery skin. Note the enlarged pectoral and ventral fins that allow them to walk.

Great White sharks from South Africa have been recorded in Western Australia. A few percentage points of energy conservation make a huge difference in these marathon trans-global voyages. Swimming styles, Push ups and Pectoral fins Wobbegongs swim by making lateral movements of the entire body from head to tail. Their skeleton is more flexible than whalers for example. Wobbegongs also do push-ups! Yes, I did say push ups. When taking off, they literally push hard off the bottom to launch themselves into motion. They also use their floppy pectoral fins for a basic kind of walking around the bottom. The Epaulette shark is a good bottom walker and has been recorded as being able to walk backwards. Next time I see an Epaulette shark up on the reef, I will watch it more

carefully to see how it can walk backwards. New research has discovered that the cartilaginous skeleton in the pectoral fin has more muscular development in wobbegongs and one less vertebral join than the more rigid Whalers. The feeding lunge of wobbies is powered largely by these big muscular pectoral fins. In fact, when Big Ornate wobbegongs get to their maximum size, the front end of the shark becomes massive. The head and pectoral fins merge into a huge front end, like an massive body builder. These big floppy flexible fins are good for acceleration and sharp turning, both are essential for capturing fish. The rigid fins of Whaler shark are better suited to cruising and sprinting. Whaler sharks swim by making lateral movements of just the rear half of their body.

A Wobbegong elevates its head, thrusts through its pectoral fin and pushes upwards to launch itself off the rocks.

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DIVE LOG Australasia #409 - December ‘24

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