Scientists Discover Novel New Way of Determining Pregnancy in Sharks

Using ultrasound on pregnant mothers might not sound like a breakthrough in scientific technology – but it is when it comes to sharks.

Two researchers in the Bahamas have managed to engineer a non-invasive method of detecting pregnancy in tiger sharks inhabiting the area near Tiger Beach, using ultrasound to test the fish without hurting them.

Marine Maternity Ward?

Generally, tiger sharks tend to congregate by size – larger specimens stick with their bulky brethren, whilst smaller sharks stay together. However, shark researcher Neil Hammerschlag, from the University of Miami’s Rosenstiel School of Marine and Atmospheric Science, noticed something unusual about the sharks around Tiger Beach.

Having dived there for several years, it came to Hammerschlag’s attention that these were almost all female and ranged from adults to juveniles. Furthermore, from the visible bulge in their stomachs, many of them appeared to be pregnant.

Intrigued, he wanted to learn more. However, the standard procedure for “learning more” about sharks is to “sacrifice” them and conduct post-mortem investigations upon their carcasses. Keen to find a more humane and less invasive way to address the problem, Hammerschlag teamed up with James Sulikowski, a researcher at the Department of Marine Science of the University of New England.

Trial and Error

Sulikowksi and Hammerschlag tried various methods of examining the sharks. Firstly, they sedated the beast and took a blood sample, but this was not able to produce conclusive results about the pregnancy nor give much in the way of other helpful information.

Instead, they tried the human technique of ultrasound. At the outset, the machine they used was too outdated and not sophisticated enough to take sharp images, but just a few years later, the wonders of modern technology solved the problem. A state-of-the-art device was able to not only deliver high-resolution images of the pup, but also offer an insight into the workings of shark reproductive systems.

Their findings were published in the journal Aquatic Biology and also detail how they have since developed better analyses techniques for blood samples, making them a viable alternative in determining pregnancy.

“What we’ve been able to do is use a combination of these techniques, so if someone doesn’t have an ultrasound and they can just grab a blood sample, they can still get useful information from it,” explained Sulikowski.

To the Future

The next step will be partly to try and drive down costs of ultrasound scanners, which are currently relatively high. Primarily, however, the team will be looking to use the data they have to better understand the mating, feeding and birthing habits of the sharks. If they are able to ascertain when and where the pups will be born, they can make arrangements to divert traffic away from the area.

Of course, human intervention is a big problem for the population of all marine life – but especially so for large, predatory fish in Caribbean reef areas. The influx of humans, along with the subsequent population boom, has led to increased competition for food.

Moreover, the leakage of chemicals such as mercury into oceans and seas infiltrate the bloodstreams of all fish exposed to them, but can accumulate in larger and more risky amounts in bigger fish such as sharks and tuna. These problems and others were discussed at the Mercury World Expo, which is intended to provide real-world solutions to the potential environmental dangers posed by mercury.