Sharks, skates and rays lay eggs?
Some species of shark and ray are similar to humans as they also give birth to live young (viviparous).However, skates and the other species of shark and rays lay eggcases to allow embryos to develop outside of the mother (oviparous).
Species such as the catshark will lay their eggs on the seabed where they can attach to a substratum (seaweed, coral or debris) using tendrils found on either end of an eggcase. Hopefully, this will keep them from being washed out into the open sea or onto land. It is here in the relatively safe habitats of coastal areas that a shark embryo will develop until hatching.
Shark eggcases are typically oblong in shape (top of picture) and will range in colour from dark brown/green to lighter shades of brown/green. Skate and ray eggcases (bottom of picture) are slighter squarer in shape and have the same leathery texture that shark eggcases possess.
You can typically find eggcases in the strand line and if you’re up for a bit of rooting around, they can be found under layers of washed up seaweed and debris. They can also be found further up the beach as loose eggcases can be blown around in the wind. Once you get your eye in, they will become easier to find!
Manxsmc will be conducting regular shark, skate and ray eggcase hunts all over the Isle of Man. This will be in conjunction with the The Great Eggcase Hunt, a Shark Trust initiative and all of our data will be reported to them to support their vital work.
When we come across a shark, skate or ray eggcase, this is the procedure we will be following:
- If the case is intact, we will make sure the eggcase is empty by holding it up to the light to see if any dark shadows are present in the eggcase and gently applying pressure to the centre of the case to feel if any embryos are inside. If there is a shadow and it is not moving, the likelihood is the embryo inside is no longer viable and will be left on the beach.
- We will record which beach it was found on (and an OS reference or latitude and longitude), the date, whether it was attached to a substrate (such as seaweed) and the recent weather conditions e.g. stormy weather or calm weather.
- The empty eggcases will be taken back to the office for pictures to be taken of them alongside a ruler.
- They will then be submerged and soaked in tap water for around 1 - 2 hours (fully dehydrated eggcases will need longer to soak, up to >24 hours in some cases). Once they have rehydrated, we will take them out of the water and photograph them once more with a ruler for scale.
These pictures will be used for verification during the identification process. Consequently, they are very important to our and the Shark Trust’s survey work.
This project needs YOU! If you’re out and about and spot an eggcase, we’d love to hear about your finds! As mentioned above, manxsmc has been recruited to send in our data and your data to the Shark Trust, so you do not need to record your sightings separately on their website as this could lead to doubling up of data which would affect results. Manxsmc will of course use your name and details if you wish; you found them after all!
If you want to and need a hand identifying your eggcases, the The Great Eggcase Huntinitiative has an excellent ID guide you can check out before sending us your info over. Otherwise we are happy to ID them for you.
If you find any whilst out walking on the beach, please follow the same guidelines as mentioned above. If you find an eggcase with a moving embryo inside please ring us on 07624 393486 or 07624 415688 immediately.
You can report your sightings here!