Shark and ray eggs in Spain: learn how to identify them and collaborate with data collection
Due to the collaboration between The Shark Trust, Sanamares, Lamna and SUBMON, a poster has been produced for the identification of shark and ray eggs in the Spanish Mediterranean and Atlantic. This initiative comes from a project started by The Shark Trust in 2003, “The Great Eggcase Hunt” in which they have already managed to accumulate in their database records of hundreds of thousands of eggs around the world, making it one of the citizen science projects on elasmobranchs with the most data recorded (currently more than 350,000 records). Thus, through the collaboration of these four organisations, The Shark Trust’s materials have been selected and translated to adapt them to the species that can be found on the Spanish coasts and, therefore, continue to contribute to the knowledge of these species.
Where can shark and ray eggs be found?
First of all, it is important to know that not all sharks and rays lay eggs as, over many years of evolution, some species have developed different ways of reproduction. Some of these species are oviparous, and we are going to focus on this group of species. In Spanish waters, only the species of true rays (Family Rajidae) and the group of catsharks (Family Scyliorhinidae) are oviparous. Once they have laid their eggs, they hatch months after and their empty capsules often end up on beaches, especially after storms. These capsules are usually found at the breaking line of the waves, relatively close to the water, so we can see them during our walks along the beach.
On the Atlantic coast, where there are tides, you can also take advantage of low tide to find eggs among the algae that are exposed.
Another way of finding eggs, although it is much more difficult, is diving. In this case, it is necessary to make sure that the egg is empty and, if it is not, or if there is any doubt, simply take a photograph without disturbing the egg and, from the photograph, identification and registration can be made. Never handle an egg with a live individual inside.
Eggs of each species have different characteristics, so knowing their shape, measurements and unique qualities helps in their identification.
Tip: often, eggs found on beaches suffer from severe dehydration from the sun and wind, which changes their shape and can make them difficult to identify. In these cases, simply submerging the egg in water for an hour or two helps to rehydrate it and the egg returns to its original shape, which will make it much easier to identify.
What is the purpose of keeping a record of the eggs that appear on our coasts?
Identifying and recording the eggs that we find on beaches helps us to identify the different species and understand their presence and distribution along our coasts. This information can also be combined with other available information and validate the presence of these species in our waters.
Who can participate?
As this is a citizen science project, anyone, regardless of age and education, can collaborate on the project. Eggs, as we have explained, can be found on any beach and at any time of the year, so you can take advantage of walks on the beach or diving trips to try to find them.
In addition, citizen science projects open the door to awareness-raising and dissemination, helping more people to become interested in shark and ray populations, to learn more about the marine environment from our coasts and to become more concerned about their conservation. Activities like this can be done perfectly during family outings, encouraging children to look for and learn more about these wonderful animals.
How can you take part?
Download our PDF poster to help you with the identification and register the eggs you find (current or old) on The Shark Trust website www.eggcase.org.
You can also send your records (with the measurements of the egg and the location area) to the citizen science Facebook group “Sharks and rays of the Western Mediterranean” that Associació Lamna and SUBMON manage together, where we can help you to identify them. All the records we obtain through our page will also be sent to The Shark Trust’s database.
Finally, we would like to thank The Shark Trust for their invitation to collaborate in this initiative, as well as Lamna and Sanamares for their collaboration.