Intriguing Beach Finds: mermaid’s purses

On a blustery day, last November, I was walking along Moeraki Beach with some friends when we came across dozens of these strange black things. They are colloquially called Mermaid’s purses, which doesn’t give much clue as to their real identity. But my friends guessed they’d be shark or ray eggs. So I posted them on iNaturalist to find out.

We discovered that the first two images are the egg cases of Elephant fish, also known as Elephant sharks or Australian ghost sharks.

And the third one, is the egg case of a Carpet shark.

iNaturalist is a great tool for identifying living things. Scientists can use the data that people enter too, to find out more about the distribution of living things.

It also includes images of the actual sharks, which are fascinating to see.

Elephant fish on iNaturalist

While some large sharks give birth to live young, others lay eggs which then hatch outside of the mother’s body. Often these eggs have tendrils that will entangle in seaweed or flanges that help them get wedged among rocks on the sea floor. That gives the baby shark a chance of hatching in a safe place.

Port Jackson Shark Egg Case with tendrils and flanges - seen on a beach in Australia

The sharks that we found egg capsules from are not dangerous to humans, they are all bottom-feeders, like the shark below, that I found dead on a beach.