Judith Bakker collecting samples

Can we use environmental DNA to investigate shark populations?

Judith Bakker, a Ph.D. candidate at Salford University in Manchester, England, was conducting shark research in The Bahamas last week with support from the Bimini Biological Field Station, often referred to as the Sharklab.

Bakker is developing methods for scientists to be able to collect environmental DNA, or eDNA, and to test it for the presence of shark species.

The study is funded by The Pew Charitable Trusts, the Washington, D.C.-based non-government organization that worked closely with The Bahamas National Trust and the government to create a shark sanctuary in Bahamian waters in 2011.

eDNA is made up of DNA shed by animals and anything else that lives in the sea, this DNA can be either free-floating or bound to particulate matter found in the water column.

“We should be able to detect tiny bits of shark eDNA that have been released from their feces poop, urine, blood, semen, mucus or skin cells or other tissues,” explains Bakker.

The scientist collects several gallons of water from different types of habitats including mangroves, deep water, the Gulf Stream, and at popular shark dive sites around Bimini.

Judith Bakker at work

She then takes the water samples back to the lab where she runs them through a two filter using a vacuum pump. Filters with two different pore sizes are used, which capture anything in the water larger than 0.22 and 0.45 micrometers, respectively. This is about the size needed to capture the eDNA. Once she collects the eDNA on the filter, she extracts the DNA, which is then sequenced to test for the presence of sharks. Like all living creatures, sharks have DNA codes unique to every species.

“Bimini is a very sharky place,” says Bakker. “If these techniques are going to work, this is the place where we are most likely to get positive results. We know that there are sharks in the water here, we just have to prove that we can detect their DNA in the water.”

“The Bahamas has taken many steps to protect sharks, and this is one of the main reasons I chose to conduct my research here,” said Bakker. “I hope that other countries do the same and create shark sanctuaries before we lose some species forever.”

Angelo Villagomez, manager of Pew’s global shark conservation campaign, accompanied Bakker during her data collection.

“This is ground-breaking work,” said Villagomez. “As this technology develops, two or three down the road, we could have the ability to test for the presence of shark species just by using a water sample. We might even be able to test for density. This could have implications for conservation and management of sharks and other species.”

Bakker has previously collected eDNA samples in Belize and Jamaica. After leaving Bimini she went to Turks & Caicos Islands to collect samples. She is returning to Manchester in March to test her samples and will have her preliminary results during the spring.

Villagomez and Bakker are hopeful that she will show that the technology is feasible.

“It’s just a hypothesis, of course,” said Villagomez. “But Judith has already successfully collected samples and had positive test results from shark eDNA extraction conducted at an aquarium, so it looks encouraging that she will prove it true.”

Caribbean reef sharks