[Port Jackson with Eggcase © Taso Viglas.]


Oviparity is a method of reproduction used by some sharks and all true skates.

This is where an adult shark lays tough leathery eggcases, also known as ‘mermaid’s purses, on the seabed. The baby shark develops inside the egg before hatching. The size and shape of these eggcases are different depending on the type of shark that laid them. Port Jackson Sharks for example lay large eggs shaped like a corkscrew, which they wedge firmly between rocks.

Skate Life Cycle © Marc Dando.

Skates also reproduce in this way. After several months of developing, a miniature skate will emerge and the empty eggcases (being much lighter) can often be found washed up on the beach. The Shark Trust’s Great Eggcase Hunt Project needs help to find these eggcases as this tells us important information about where skates are laying their eggs.