Citizen Science

The Great Eggcase Hunt

February 3, 2015

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Skate eggcase found. Photo © David Backes/Flickr through a Creative Commons license.

What Is The Great Eggcase Hunt?

Would you like to go on a hunt for mermaid’s purses?

Mermaid’s purses? No, this is not a mythical quest or the next ocean thriller a la Megalodon.

The Great Eggcase Hunt is an actual citizen science project run by the Shark Trust to find very real, but whimsically named mermaid’s purses — the eggcases of sharks and skates that wash up on the beach.

Knowing where these eggcases wash up allows conservation scientists to find the nursery grounds of skates and sharks so that they can make a case for protecting those areas.

Fifty percent (yes, half!) of all shark species in the UK are listed as threatened by the IUCN and the populations continue to decline. You can help the Shark Trust reverse that trend.

“Although the Great Eggcase Hunt was established in the UK, eggcase hunting can take place all over the world. International records have been submitted from South Africa, Australia, USA, Israel and Malta to name just a few,” Cat Gordon, a Conservation Officer for Shark Trust explains.

If you live near any ocean beach, you can get out and learn more about the sharks and skates breeding in your area.

Why Is The Great Eggcase Hunt Important?

Many shark species are apex predators, which means that they play an especially important role in keeping ecosystems healthy; by eating weak and sick creatures they keep the gene pool strong and mitigate the spread of disease.

But modern threats, especially unmanaged fishing practices, have drastically reduced many populations of sharks and skates.

The Shark Trust works through many projects including the Great Eggcase Hunt and cooperative programs with fishermen to improve practices and identify important locations to protect vulnerable species.

The eggcase of a Thornback Ray. Photo © The Shark Trust.
The eggcase of a Thornback Ray. Photo © The Shark Trust.

“Empty eggcases can provide an easily accessible source of information on the location of egglaying elasmobranch (shark, skate and ray) populations and their potential nursery grounds – identification of these critical areas can help us to propose suitable management measures,” Gordon explains.

How do you know when you’ve found a mermaid’s purse? Are they difficult to find? What about identifying species?

Fortunately, the Shark Trust’s website is packed with great resources.

Did you know that there are 35 species of sharks found in British waters alone and an additional 19 species in the North Atlantic? And don’t forget the 21 species of skates and rays! 

You will even learn to identify egg-laying species of shark or skates based on the eggcase alone. Not all sharks lay eggs; some give birth to live young.

Identification materials currently available on the Shark Trust site are currently limited to Britain and the North Atlantic, but they will be expanding soon.

“The Shark Trust is now collaborating with the Wildlife Conservation Society New York Seascape Program to create additional ID materials for Northwest Atlantic species, and to engage the US public in the Great Eggcase Hunt,” Gordon notes.

The eggcases themselves are a fascinating bit of biology.

“Everything that the developing embryo needs is within that eggcase. They absorb nutrients from the yolk sac and by using their tail as a pump, draw in oxygenated water through tiny slits in the eggcase horns,” says Gordon. “When they’re ready, the juvenile will emerge as an independent, fully formed, miniature version of the adult.”

It probably goes without saying that hunting for mermaid’s purses is a unique and effective way to get kids interested in marine science and conservation. Here are some resources for parents and teachers.

Cat Gordon of the Shark Trust and the Winsor Family on an eggcase hunt. Photo © sghaywood photography.
Cat Gordon of the Shark Trust and the Winsor Family on an eggcase hunt. Photo © sghaywood photography.

How Can You Get Involved In The Great Eggcase Hunt?

Find a nearby beach and head out to look for mermaid’s purses. They wash up on the beach at all times of year, so you don’t need to wait for spring.

Visit the Great Eggcase Hunt website to plan your hunt and for important tips on safety and recording information.

Identify any eggcases that you find. Pro tip: soak them in water first so that they expand to their full size. Record your sighting.

Recently, the Shark Trust released a Great Eggcase app.

“You can have the ID guide and encyclopedia at your fingertips and record your finds while still on the beach!” Gordon remarks. “It’s currently available for Apple devices (search Shark Trust in the App Store!) but the Android version is coming soon.”

Your sighting will appear on the Shark Trust’s map and add to their pool of data on shark species locations.

Looking for more ways to help sharks? Check out these ideas for promoting shark conservation.

Head to a beach and bring kids along for a magical experience. It’s as good as hunting for pirate treasure — maybe better — and you can learn about sharks along the way!

Lisa Feldkamp

Lisa loves all things citizen science and enjoys learning about everything that goes on four legs, two wings or fins - she even finds six and eight-legged critters fascinating at a safe distance. She has a PhD in Classical Literature and Languages from the University of Wisconsin - Madison and enjoys reading Greek and Roman literature or talking about mythology in her spare time. More from Lisa

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