No pups for ragged-tooth shark
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It was going to be the world’s first ragged-tooth shark birth ever recorded if it had happened.
But after a year watching and waiting for this marvel of nature to unfold uShaka Marine World’s team of aquarists have tossed in the cameras, the late nights and the excitement.
It all began when bite marks were noticed on 10-year-old shark, Cathy, after the aquarists had seen mating behaviour in the shark tank and it was decided once the belly had grown bigger, that she was pregnant.
Ragged-tooth male sharks bite on to females during mating and this particular ragged-tooth had since been named Miss X, because all animals at the aquarium are identified by some feature on their body, but she had none before the mating marks.
She was then isolated from the other sharks using a huge net as a barrier to stop her young being eaten by the other sharks.
Then the waiting began.
Ragged-tooth sharks have two uteruses where there are a number of eggs. Only one in each uterus hatches and remains in the uterus, feeding off the other eggs. The female can release unfertilised eggs to continue feeding the pups.
“We don’t think she is pregnant anymore, her belly has reduced in size and a year has gone by,” said Jone Porter, the director of education at uShaka.
She said the dud pregnancy could be attributed to two things: it could be that the eggs were not fertile, and then the shark just absorbs the tissue to save her the energy of having a miscarriage like humans.
“Sharks also grow according to temperature around them. The warmer it is, the faster they grow. It could be that the temperature was just not right,” she said.
A sonogram (ultrasound) could be done to determine whether the shark is still pregnant, but if Miss X were still to be pregnant and was distressed in any form, she could lose her young.
“We were convinced that she would give birth at night when no-one was around so once in a while when staff were working late they would go and check on her, it’s still something we do,” Porter said.
She said some visitors at the aquarium would ask whether being confined to a small space was not distressing the pregnant shark in any way.
“When ragged-tooths are pregnant they don’t swim, they go into caves or overhangs and they wait there,” she said.
Ragged-tooths mate off Scott-burgh.
“They then swim to Mozambique, where they spend the waiting period, and just before giving birth they swim to the Eastern Cape where they give birth,” she said.
Ragged-tooths are on the international red data list of threatened species.
“Some sharks lay 50 eggs and reproduce every year. Ragged-tooth sharks only start to produce in the fifth year of their lives,” Porter said. And then there are only two pups at a time.
Staff had changed their routine during the “pregnancy”, she said.
“We have had to work around her and we were lucky to have staff that were doing this purely for the love of it. The staff wanted to give the best and they all went beyond their normal job description.”