Cape Catsharks – curiouser & curiouser

A pyjama party: catsharks are social animals and sleep in piles under convenient overhangs (Jean Tresfon)

Mention Cape Town diving and the conversation turns inevitably to sharks. By ‘sharks’ people usually mean the big toothy brutes which are firmly, if irrationally, believed to spend their days cruising in search of a feast of tender human flesh.  These same people are also usually slightly incredulous to discover that though there are many sharks seen around the Cape Peninsula by scuba divers, the sight of them is extremely rarely traumatogenic.

Text by by Georgina Jones

This is because most of the sharks seen around Cape Town are small and more likely to inspire the ‘oh cute’ reflex than a mental replay of the soundtrack from ‘Jaws’. They are part of a big group known as catsharks, the Scyliorhinidae. About 100 species are found worldwide in tropical and temperate waters, although catsharks are usually found in very deep water. We are fortunate around South Africa not only to have 16 species in our area, 11 of them endemic to the region, but also, that several of them are inshore sharks so that, as divers, we have the pleasure of seeing them bustling about the reefs and wrecks on their business.  Around the Cape Peninsula, four species are commonly seen.

 

 

 

 

 

 

 

 

 

 

 

 

A pair of pyjamas (Jean Tresfon)

The biggest of the four is the distinctive pyjama catshark (Poroderma africanum), growing up to a metre in total length. As one might guess from the name, the pyjama catshark is striped. Its close cousin is the leopard catshark (Poroderma pantherinum), and unsurprisingly, it has leopard-like rosettes and spots arranged in stripes on its body. Rather like its namesake, the leopard catshark is very much a creature of the night and is only rarely seen during the day, preferring to while away the daylight hours sleeping under overhangs or in caves before setting forth to hunt for its prey.

A pyjama catshark at ease (Jean Tresfon)

Their smaller cousins are the puffadder shyshark (Haploblepharus edwardsii), a lovely golden-brown creature marked with several white-spotted saddles; and the dark shyshark (Haploblepharus pictus), which is more often seen on the Atlantic side of the peninsula. This is a stockier animal, having dark saddles which may have yellowish spots.  These sharks are all oviparous, which is to say their young develop in egg cases, which the females lay in pairs. Mating is a vigorous affair, with the male biting the female on her pectoral fins to hold her in position so that he can insert his claspers. Though the females often show signs of skin damage post mating, they seem untroubled, swimming off afterwards without hesitation. It is the males who come off the worst, with older males showing signs of scarring and calcification on their claspers. Clearly male catsharks are made of stern stuff.

 

A puffadder shyshark going about its business on a Cape reef (Geoff Spiby)

In due course the female will lay a pair of eggs in cases known as mermaid’s purses. Females can sometimes be seen with tendrils trailing from their bodies. These are part of the egg cases and after while, they seem to irritate the female, which goes in search of an upright support such as a sea fan and begins to swim around it. This causes the strings to catch on the support and the circular swimming helps to gradually pull the egg case out. The yolks are easy to see through the surface of the egg case, and occasionally the embryonic shark can be seen wriggling inside as well. The egg cases are a potential feast for carnivorous snails, octopus and other sharks. The lucky occupants which avoid the attention of predators emerge after 3-6 months, biting their way out of the egg cases and setting off to seek their own prey. They are very small at this stage, all of them smaller than 15cm, and frequently become another predator’s dinner. If they manage to escape from the many hungry mouths on the reefs, they feed on small bony fishes, crustaceans and octopus and may live for over twenty years.

 

A puffadder shyshark peers out from a dense forest of feather stars (Geoff Spiby)

This group is also known as shysharks because of its members’ habit of curling up into a ball with their tail or pectoral fin over their eyes when threatened. It is possible that the purpose of this action is to produce a bigger shape which is more difficult for a predator to swallow. Given that the total diamater of the ball is often not much over 20cm, this probably doesn’t discourage
many predators other than the smaller ones. It does raise their cuteness factor though. So yes, Cape Town diving, sharks, lots of them. But scary sharks? No.

 

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