EGGCASE CHAMPION TRAINING GUIDE
THE SHARK TRUST
We work to safeguard a future for sharks, skates, rays, and chimaera (hereon ‘sharks’) through positive change. The Trust achieves this through science, education, influence, and action.
For over 25 years we have worked at the forefront of shark conservation, with a focus on fisheries management and species protection. We are UK-based but globally active. Working with collaborators and partners across the globe.
WE ARE THE SHARK
TRUST VIDEO
SHARKS, SKATES, RAYS, AND CHIMAERAS
There are over 1200 species of shark, skates, rays, and chimaeras (Class: Chondrichthyes) globally.
Reproductive modes vary according to species: Some species are viviparous and bear live young (as with mammals).
Some are ovoviviparous, where embryos develop within a thin eggcase but are retained inside the female before hatching and being born as if they were born as live young.
Others are oviparous (egg-laying), and embryos develop within toughened eggcases that are deposited on the sea floor or attached to seaweed.
©Fiona Ayest
© Simon Rogerson © Goose van der Heide
© Sally Sharrock
© Stephen Childs
THE GREAT EGGCASE HUNT
A CITIZEN SCIENCE PROJECT FOCUSED ON RECORDING SHARK EGGCASES
Established in 2003, the Great Eggcase Hunt is the Shark Trust’s flagship citizen and community science recording project. It encourages participants to search for eggcases that have washed ashore, or report those seen by divers or snorkellers developing underwater.
By recording shark and skate eggcases, we can gain a better understanding of the presence and diversity of oviparous (egglaying) species in British waters –and beyond!
The Great Eggcase Hunt has evolved over the years. With project partners established in the Netherlands, Portugal, and Australia, and eggcase submissions recorded from far and wide around the world! Regional identification materials have also been created for a number of other areas – with others in development.
In 2022 we launched a brand-new citizen science app to help people discover more about sharks and contribute towards all of the Shark Trust’s citizen science projects (while collecting reward cards!). And now, we are proud to be putting together this guide. To empower people to take part in the Great Eggcase Hunt and become Eggcase Champions - all while educating and inspiring others to get involved.
Citizen Science
Defined as: the collection and analysis of data relating to the natural world by members of the general public, typically as part of a collaborative project with professional scientists.
A Nursehound (Scyliorhinus stellaris) eggcase from Anglesey, Wales © Sally Aston | GEH
Some sharks, and all true skates and chimaeras, reproduce by laying eggs. These are surrounded by a tough capsule made of collagen that protects the embryo as it develops inside. After several months these are ready to hatch, and a fully formed shark, skate or chimaera will emerge.
Once empty, the eggcases (or mermaid’s purses) often wash up on the beach. The eggcases of different species vary so, by looking at the size, shape, and features, it’s possible to identify which species laid it.
Key eggcase forms:
There are five key groups (or Orders) of Chondricthyans that lay eggs. The eggcases from each Order have specific traits that can help you work out from which group it comes.
These key Orders are:
CATSHARKS
Elongated and almost oblong in shape, often with long curly tendrils attached to each corner.
SKATE
Rectangular or almost square with a dinstinctive horn at each corner, although this can be masked by keels or aprons on some eggcases.
CHIMAERA
Leaf or spindle shaped, with a fringe running around the outside. On some species this is very narrow, and on some species it can be several centimeters wide!
HORNSHARKS
Spiral or corkscrew in shape, some species do have tendrils!
end
keels
end
CARPET SHARKS
More oval or rounded in shape, often with three horns.
(upper) horns
(lower) horn
The development or incubation period for catsharks and skates takes 5-12 months (sometimes it can take a little longer) depending on the species.
1. The adult female produces eggcase surrounded by a tough capsule.
Eggs are laid (often in pairs, one from each ovary) by the female at daily or weekly intervals.
Eggs are usually anchored onto the seabed using mucus filaments, or attached to seaweed by curled tendrils.
2. The embryo starts to develop inside the egg by feeding on the yolk sac.
3. Small slits along the horns allow oxygenated sea water to enter and waste to exit.
As the embryo grows, the tail curves up the side of the eggcase; developing embryos pump sea water into the eggcase by beating their tails. For skate, the pectoral fins fold up over its back as it develops.
Gills develop externally.
4. Once the young have fully absorbed the yolk sac, the shark or skate emerges from between the upper horns or tendrils of the eggcase and hatches as a miniature version of the adult.
5. The juvenile will continue to develop to adulthood and, once mature, the adult female will produce her own eggs and the process is repeated.
Left: the skate life cycle ©Marc Dando Below: the catshark life cycle © Musa SM, Czachur MV, Shiels HA (2018)
A Nursehound (Scyliorhinus stellaris) eggcase and embryo © Rick Bruintjes | GEH
ORGANISING AN EVENT
If you’re running an organised event, possibly through a marine centre, NGO/charity, aquarium, or as a school activity, then there are a few things to consider:
Check the tide times when planning the date and time of your event to ensure you make the most of the beach.
Complete a risk assessment in advance and carry a first aid kit as a precaution.
Make sure you (or the organisation you are doing an event for) have the appropriate Public Liability Insurance to run an event.
Advertise your event – if it’s a public event, tag us on social media so we can share the event in case we have any followers in the area who may be interested in participating!
Download and print the eggcase ID guide We have some hard copies of the British Isles/Northwest Europe ID guide along with Great Eggcase Hunt stickers, so drop us a line (eggcase@sharktrust.org) and we may be able to send some resources to you.
Decide whether participants are going to record their own eggcases or if you’ll take on the responsibility as the organiser – if the latter, then make sure you note how many people came along so you can include that in your submission.
When submitting records, there is an ‘organisation’ field where you can enter your organisation or project’s name (e.g., Project SIARC, Wild Coast Sussex etc.) so we can easily extract data if required, and keep a tally of who our top recording projects are!
Disclaimer: the Shark Trust is not responsible for events run by other organisations or individuals - please make sure you have the appropriate insurance to run an event and have conducted a thorough risk assessment.
© Project SIARC / NWWT
SCAN TO SEE OUR ID GUIDES including translated and regional resources
© sghaywood photography
HOW THIS GUIDE WORKS
The Great Eggcase Hunt is based on four main themes:
SEARCH IDENTIFY RECORD DISCOVER
This guide follows the same structure. Each section covers in-depth what you need to do to take part in the Great Eggcase Hunt. The guide includes videos and buttons to take you to downloads and other relevant sections/pages.
If after your eggcase hunts you want to find out more, or to see our results so far, you can find out more information on the ‘Discover’ pages of our website. RECORD
TIME TO FIND AN EGGCASE!
Next time you’re at the beach looking for eggcases remember these easy steps:
SEARCH for eggcases in the strandline or caught in grass at the back of the beach.
IDENTIFY your find(s) by following the tips below, and using the ID guide relevant to your region. Scan the QR code for our ID guides...
ID GUIDES
RECORD your find(s) via one of the options below – remember to upload some photos!
Be safe, keep an eye on the tides, & have fun!
TOOL KIT
GOOD WORK! YOU’VE FOUND AN EGGCASE... WHAT NEXT?
By reporting any eggcases that you find to the Shark Trust’s Great Eggcase Hunt you can contribute to science and help further our understanding of oviparous (egg laying) sharks, skates & chimaeras. Mapping where different species are seen helps us understand how they live, and therefore how we can act to better protect important areas such as egg laying grounds.
DID YOU KNOW...
Eggcases are called ‘mermaids purses’ because they feel like leather & open at one end – just like a purse!
BUCKET SCIENCE
Soak your eggcase for 24 hours to make it easier to ID
left: The GEH cover page - one of the resources available to help you with running (or takng part in) a Great Eggcase Hunt event
MEET THE EGGS-PERTS
With this guide, two of the Shark Trust’s conservation team will take you through everything you need to know to get up and running with the Great Eggcase Hunt.
Cat and Harriet are experts in all things eggcase. Cat has developed the proje8ct from 2010 into what it is now. Whilst Harriet has been working on wrangling the data since spring 2022.
CAT HARRIET
CAT GORDON SENIOR CONSERVATION OFFICER
Cat has well over a decade’s experience working in shark conservation, with a focus on species protection for threatened sharks/skate and citizen science. She’s been Project Manager for the Great Eggcase Hunt for much of its creation and has seen it evolve and expand, welcoming records from far beyond the UK.
She can’t step on a beach without her eyes scanning the strandline for the tell-tale horns or tendrils of an eggcase. It’s always a competition to see who can find the first eggcase when she’s around!
Harriet Allen Citizen Science Data Officer
Harriet is responsible for the data management and analysis aspects of the Shark Trust’s citizen science projects - she checks all the records that come into our projects, including the Great Eggcase Hunt, the Shark Log - shark sightings database, the Basking Shark Project, the Shark and Ray Entanglement Project (led by the University of Exeter), and our yearly Great Shark Snapshot.
She’s not intimidated by a spreadsheet and will quickly bring even the most disorganised dataset into order (trust us, we’ve been challenging her!). She also puts together project reports and summaries for the Great Eggcase Hunt, showcasing all the fantastic finds from our Citizen Scientists!
The first step is to hit the beach in search of eggcases!
Check out the project results maps to find out if any have been found in your local area. This may help you get an idea of where is a good place to go searching, or you may want to try and find eggcases in a region where we haven’t had any reported before!
SEARCH VIDEO
TIPS
Eggcases can be found all year round (they may have been lying empty for some time before being dislodged so may not always be freshly hatched).
The best places to search are…
• Amongst the seaweed in the strandline
• At the back of the beach
• In grass/sand dunes
Stormy weather washes up lots of seaweed and strandline treasures, so after it’s passed and when it’s safe to do so, it’s a great time to go hunting.
Check to make sure it’s an empty eggcase and nothing is inside. If it’s hatched, you should be able to see an opening between the upper horns. If you hold the eggcase up to the light you can sometimes see if anything is still inside.
HINTS AND TIPS:
Check tide times so you don’t become stranded.
Use a stick or boot to rummage in seaweed to avoid any nasty surprises.
Be respectful of wildlife and habitats and don’t take any living organisms home.
►Take 5! While you are on the beach, help out by picking up five pieces of litter and removing them from the beach.
Once you’ve found your eggcase(s), it’s time to identify your finds!
REMEMBER:
Soaking them in water first may make identification easier. Look closely at:
• Different features - including horns, tendrils, and keels.
• Size – eggcases can vary from 4cm to 20cm!
• Shape – oblong/elongated (catsharks), square/rectangular (skate), spiral/corkscrew (horn shark), oval/rounded (carpetshark), spindle/leaf shaped (chimaera).
IDENTIFY VIDEO
TROUBLESHOOTING:
Broken eggcases - horns and tendrils are delicate so may break off by the time they are stranded and you find them on the beach – sometimes it’s obvious that bits are missing, but sometimes it can be misleading, e.g. Smallspotted Catsharks without their tendrils could easily be mistaken for Blackmouth Catsharks which are much less likely to wash ashore.
Colour - try not to use colour as an indicator as this varies greatly. Fresher skate eggcases can have a green tinge to them, but become darker brown/black. Smallspotted Catsharks can vary from amber, to brown, to dark green, to black.
Misshapen capsules - older eggcases won’t rehydrate so well so may still be a bit warped and not expand to their original size.
Size - the range of sizes indicated on the ID guides are approximate so you may find some species that are smaller or larger than stated.
FOR EGGCASES FROM THE BRITISH ISLES AND NORTHWEST
There are 13 eggcases that wash up most commonly around the British Isles and Northwest Europe. There are other egglaying species in this region, but these tend to be deeper and so the eggcases from these species are less likely to wash ashore. By looking at the key features for each eggcase you can identify which species it comes from.
Here is how to distinguish between the eggcases in this region:
FOR MORE INFO ON IDENTIFYING
EGGCASES FROM THE BRITISH ISLES AND NORTH WEST EUROPE SEE OUR GUIDE BOOK AND TRAINING VIDEO:
BRITISH EGGCASE ID GUIDE
Smallspotted Catshark (Scyliorhinus canicula) eggcases from Cornwall
© Peter McGregor | GEH
A Thornback Ray (Raja clavata) eggcase from Cumbria
© Charlotte Rankin | GEH
EUROPEAN AND MEDITERRANEAN ID GUIDES
British Isles and Northwest Europe
(English | Cymraeg)
Netherlands
Portugal
Türkiye
Spain
Greece
Libya
Tunisia
OTHER EUROPEAN AND MEDITERRANEAN RESOURCES
Step-by-step ID key (English | Cymraeg)
British Isles and Northwest Europe digital leaflet
PUPS RESOURCES
British Isles and Northwest Europe
Junior ID guide
British Isles and Northwest Europe
Junior digital leaflet
Indoor Junior eggcase hunt
Eggcase Workbook (coming soon!)
AUSTRALIA
See the Great Eggcase Hunt Australia landing page at: sharktrust.org/greateggcasehunt/geh-australia
United States of America
Eastern Seaboard (North Carolina)
OTHER
RESOURCES
RECORD
SUBMITTING YOUR FINDS TO THE GREAT EGGCASE HUNT
The final step is to record your find(s)!
There are several ways to submit your eggcases:
The Recording Hub
The Shark Trust mobile app
RECORD VIDEO
HINTS AND TIPS
Photographs - take an image of all your eggcases (a group photo is fine, or multiple images) so that we can verify your finds. Make sure that your eggcases are laid out neatly without overlapping.
Include ALL your eggcases - make sure to include every eggcase in the image or images that you upload - this way we can check count and species ID. If you can, group the eggcases by species (or similar looking eggcases)!
Scale - include a ruler or a coin for scale in the photo.
Notes - if you have anything you want to tell us, or ask us, make use of the notes section!
The Shark Trust App
The perfect companion to your Great Eggcase Hunts!
As you submit your findings across the Shark Trust’s citizen science projects, you will build a record of your research contributions. These are saved in your profile and shared with the wider community, so users can see what other people are discovering.
Alongside this important citizen science aspect, there are also 50 digital shark cards to collect as you submit records!
A Blonde Ray (Raja brachyura) eggcase, an Undulate Ray (Raja undulata) eggcase and a Cuckoo Ray (Leucoraja naevus) eggcase from Jersey © Sudi Chiang | GEH
scan me SCAN TO DOWNLOAD THE APP
The Recording Hub
Head to our Recording Hub where you can provide the details of the location and date, species found, and upload your photos recording.sharktrust.org/ scan meRECORDING FORM
If all else fails, you can send us your eggcase finds via email at eggcase@sharktrust.org
Remember to include photos as well as the location, date and how many you found!
SOCIAL MEDIA
Remember to shout about your eggcase finds on social media! Tag us in @ SharkTrustUK (twitter) or @TheSharkTrust (Facebook and Instagram) and use #GreatEggcaseHunt.
On Instagram you can even search for the Shark Trust and Great Eggcase Hunt gifs to use on your stories!
Records have been flying in from around the world for 20 years!
To date, the Great Eggcase Hunt database has records of over 440,000 eggcases from 49 species and 30 countries!
In addition, the Shark Trust has received images and specimens sent by colleagues from fish markets, surveys, museums, and aquariums, as well as those from interested members of the public around the world.
Check out our recent report summarising all the finds from the last 20 years:
An Elephant Fish (Callorhinchus milii) eggcase from Tasmania, Australia © Miriam G | GEH
Find out more about what our citizen scientists have been submitting!
We regularly put out reports summarising the recent finds from the Great Eggcase Hunt, so keep an eye on the Great Eggcase Hunt webpage for the most recent project summary! Take a look at the latest project report and find out what’s been happening.
Alternatively, check out the online results maps to see where we’ve had records from, or to check the maps for some of our most commonly reported species.
This data will soon be open access!
If you would like to use this data for your own research or project, the data compiled as part of the Great Eggcase Hunt will soon be open access and available for download.
If using the Great Eggcase Hunt data in your work, please reference that this data is complied from the "Shark Trust’s Great Eggcase Hunt”.
If you would like an updated version of this dataset, including the records from the last year, please get in touch at eggcase@sharktrust.org
Other publications
Data from the Great Eggcase Hunt has also contributed to scientific publications:
Gordon et al 2016 - Descriptions and revised key to the eggcases of the skates (Rajiformes: Rajidae) and catsharks (Carcharhiniformes: Scyliorhinidae) of the British Isles.
Ellis et al 2024 (in prep) - The distribution of juvenile stages and eggcases of skates (Rajidae) around the British Isles.
All eggcases reported to the Great Eggcase Hunt from around the British Isles 2003 - 2023.
The size of the pie shows the number of eggcases, and the wedges show the proportional composition of species reported from each region.
Map from the Great Eggcase Hunt 20 Year Report (2023).
Thank you for taking part in the Great Eggcase Hunt!
You’re now well and truly part of the eggcase family and on your way to becoming an Eggcase Champion!
Whether you’ve submitted one eggcase or a hundred, this project wouldn’t be possible without you and we’re so grateful that you’ve decided to take part.
Happy eggcase hunting!
© Judith Oakley