Sharks play an essential rol in the health of our oceans

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Transmitting thornback rays (Raja Clavata) send valuable information!

The thornback ray belongs in the habitat along the coasts of the Netherlands and Belgium, but has almost disappeared here due to overfishing. The species still occurs around the British coasts.

But would the Western Scheldt now be suitable to bring back the thornback ray? Can this species survive there?

 A club of nature conservationists and researchers asked this question and started working on it. Between 2016 and 2018, hundreds of ray eggs were hatched and bred to young thornback rays, and released into the wild at an age of around one years. Of these , 30 animals were fitted with acoustic transmitters in 2018 and released in the Western Scheldt.

 

The first results are promising! 

Of the 30 sting rays, 28 were recorded by means of acoustic signals from the transmitters: they thus survived the adventure. Furthermore, we see on the picture the movements between the antennas of seven of these 28 sting rays. From this we can deduce that the animals can still swim nice distances: they show a varied movement pattern and seem to thrive under conditions in the wild.

The study uses the LifeWatch observatory set up by VLIZ and INBO, funded by the Scientific Research Fund as part of the Belgian contribution to LifeWatch. This system has antennas attached to the buoys in the Westerschelde and the Belgian part of the North Sea. As soon as a thornback ray swims along a buoy, it is observed. Among other things, the study results mean that the fishing pressure in the area may have declined somewhat.

What can you do if you catch or observe a tagged marked thornback ray?
Feedback about tagged rays is most welcome and will be rewarded with a small renumeration, a T-shirt (S till XXXL) or a nice ‘ray photo mug’ at your own choice. And of course the eternal thanks from our team of clever researchers.

How to report?

When a ray with a tag has been caught or observed you are asked to follow this step-by-step plan:
1. Write down the numbers on the tag.
2. Take a photo of the thornback ray with a ruler or an object of which the dimensions are known (preferably a coin).
3. If possible, weigh the ray and write down the weight.
4. If possible, record the gender of the ray.
5. Put the thornback ray back into the sea (for a follow-up of the study).
6. Enter the information obtained in steps 1 through 4 on the form on www.sharkray.eu.
Notifications are rewarded. You can choose from 10 euros, a ray coffee mug or a nice T-shirt.

 


This project is a collaboration of 5 organizations, namely the World Wildlife Fund Nederland, Blue Linked, the Dutch Shark Society, Sportvisserij Nederland, and the North Sea Foundation. This project also cooperates with international partners (in Ireland, Scotland, Belgium) and professional and sport fishers. The main pillars of this project are greater protection for sharks and rays in the North Sea, making fisheries more sustainable, so that there are fewer sharks and rays as by-catch, and the restoration of populations of sharks and rays in the North Sea by breeding sharks and rays with innovative projects. The first animals were released in the Oosterschelde on 14 October 2017. Sharks and rays are indispensable for a healthy North Sea with high biodiversity, but their numbers have deteriorated significantly in recent decades. The recovery pilot project involves thornback rays, a species that is easy to breed and less threatened than some other species of rays and sharks.

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