Scientists have successfully artificially inseminated bamboo white-spotted sharks, giving birth to 97 fish. This is the largest attempt to date to breed sharks in this way and could help to conserve them.
This was reported by the Field Museum of Natural History in the US city of Chicago.
Due to water pollution, climate change and industrial fishing, shark populations have declined by 71% between 1970 and 2018, and half of their species (16 of 31) are threatened or endangered, the authors of an earlier article in the scientific journal Nature estimated.
Scientists are therefore looking for ways to help both conserve and breed sharks. Transferring the fish from one aquarium to another for mating is expensive and can be stressful for them. Artificial insemination therefore seems more promising.
Different sharks have their own fertilisation patterns: females of some species, for example, can hold sperm for months, fertilising their eggs with it ‘on demand’ by the male – so he is not necessarily the father of the sharks that are born.
Some females are even able to self-fertilise their eggs (this process is called parthenogenesis), with the consequence that sharks are only born with the mother’s genetic material.
So scientists decided to focus on one species, the bamboo white-spotted shark. They reach a meter in length, often live in aquariums, have a nocturnal lifestyle and are completely safe for humans.
The researchers took 82 sperm samples from 19 males, from which they then selected high-quality samples. Some of these were used to fertilise females at Field’s Natural History Museum, while others were frozen and sent to several other places where female sharks live.
Fertilisation was carried out as follows: first, the female was checked to see whether her eggs were already fertilised (by passing light through the egg sheaths on her body), then she was put to sleep and the sperm was injected into her reproductive tract. The whole procedure lasts up to 10 minutes and is completely painless.
A total of 20 female bamboo white-spotted sharks were artificially inseminated. Four months later, small sharks – 97 fish in total – hatched from the eggs. The success rate of the procedure when using unfrozen semen was 27.6%, but when frozen for 48 hours it was only 7.1%.
Preliminary results allow scientists to hope that artificial insemination may be a viable way of breeding sharks. Such research has been done before, but it has never involved more than a few females.
Now the scientists plan to repeat it on other shark species. They published the findings in the May 13 edition of Scientific Reports.