Magicats – Witches cats
12 October 2024
Magicats – Why do witches have cats? The popular image of a witch wearing a
Have you seen one of these before? It’s a zebra shark (Stegostoma fasciatum).
Actually I THINK you’ll find zebras and sharks are two very different animals, ed
Very funny. In fact, this creature is only called a zebra shark because the pups are born with black and white stripes. They’re not closely related to zebras, in fact, they’re not that closely related to any other animal, because zebra sharks are the only member of the Stegostomatidae family.
Awww. That’s sad.
It is, isn’t it? And that’s not all. The reefs and lagoons of the Indo-Pacific Ocean should be a paradise for the zebra shark. Within their environment they are apex predators. That means their presence plays a crucial role in the health of their ecosystem. But their numbers are going down quickly. Habitat loss and unsustainable fishing practices have meant that the zebra shark is now highly endangered!
There is some good news, though. Here at The Deep aquarium in Hull, Yorkshire, we’ve housed zebra sharks since 2003 and we’re proud to be contributing to an important European breeding programme. Our aim is to protect this endangered shark for the future. Want to know how we do it?
Do I? Of course I do!
The biggest shark found in UK waters is the basking shark (Cetorhinus maximus). Adults can reach up to 8 m in length! You won’t find a basking shark’s egg case on any British beaches. Why? Because it gives birth to live young. You don’t need to worry about getting eaten by one either. Luckily for us it only eats microscopic zooplankton. Phew!
Zebra sharks are what we call oviparous; that means ‘egg-laying’. Females can lay an average of 40–80 eggs per year, but not all those eggs will result in young. Some are laid empty, and others will not go on to develop an embryo.
In deepwater reefs, the female zebra shark secures the large, brown, leathery egg cases (sometimes called mermaid purses) to rocks, using strong trailing silken fibres. In a tank, this process is slightly trickier. Our team has to work hard to get the developing pups through this delicate phase of their lifecycle.
So what do you do?
We remove the eggs and transfer them to a special incubation tank. There we can monitor embryo development and make sure all the conditions are just right. The eggs are also candled fortnightly.
YOU BURN THE EGGS?
Absolutely NOT. Candling means using a high-powered torch to see through the egg case and check that the embryo is developing properly. Zebra sharks develop in their egg cases for around six-and-a-half months, then they hatch!
Pups are born with black and white stripes. It’s believed the stripes help to keep them safe in the wild because they mimic those of the venomous banded sea snake. As the pups grow, their colour slowly changes to pale yellow and their stripes begin to break up, forming pale brown spots.
As they become juveniles, our zebra sharks are offered a diet to rival any top class seafood restaurant; squid, mussels, clam and shrimp are all on the menu. No big portions though – we feed them little and often to prevent them from gorging themselves.
We adjust their dietary needs as they grow and continue to monitor their weights, feeding them carefully until they are around one year old, after which they begin to feed once a day. Looking after these creatures certainly has its challenges, but it’s a very rewarding job. All the zebra sharks we hatch and rear here at The Deep will go on to join other aquariums as part of the European Association of Zoos and Aquariums (EAZA) breeding programme.
Aquariums like The Deep are working hard to uncover the secrets to successful shark breeding. With numbers falling rapidly, our efforts might prove to be their saving grace.
OK, so the zebra shark isn’t native to UK waters, but did you know that there are over 40 shark species frequenting the British coastline – including some of the fastest, rarest and largest in the world?
The Great Egg Case Hunt is a project set up by the Shark Trust to generate interest, knowledge and awareness of the sharks and rays native to the UK.
Shark egg cases regularly wash up on our beaches and they are a valuable source of information. Using distinctive features such as colour, size and shape, we can identify the species it came from. This data feeds into the Shark Trust database, providing scientists with a crucial insight into where potential nursery grounds are located and their population numbers. This information can help marine conservationists work out what needs protection and where!
Undertaking an egg case hunt is a great way to contribute to shark conservation. We would love more beachgoers to help collect vital data to better protect these species. Find out more information on this at: https://www.sharktrust.org/great-eggcase-hunt
If you enjoyed this interesting blog, then join AQUILA today for more!
Words: The Deep Aquarium, Hull (www.thedeep.co.uk). Illustration: Kieran Blakey
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