Key points
- We've worked with a giant aquarium in Western Australia to test ways to detect fish using the water they swim in.
- We're perfecting ways to collect DNA to detect species.
- We're using techniques normally used to sort blood cells in medical diagnostics to sort fish cells from water and count the individuals present.
There are plenty of fish in the sea but how can you count stock levels or protect endangered fish without seeing or catching them?
For research scientists Dr Haylea Power and Dr Cindy Bessey from CSIRO, Australia’s national science agency, seawater itself holds the memory of what lives beneath the surface.
They’ve been working in the Aquarium of Western Australia (AQWA)’s mesocosm, a giant tank filled with 3 million litres of seawater to test new ways of detecting fish species and identifying the presence of individual fish from the traces they leave behind.
“The tank at AQWA mimics a natural ecosystem that aquarium visitors can experience from within the underwater tunnel or from above in the glass-bottomed boat,” says Mr Matthew O’Malley, Head Curator at AQWA.
“Mesocosms like ours are hard to find elsewhere. We know exactly what’s in the aquarium, from the 50 species of fish right down to the items we feed them, which is why it’s so useful for science.
“We’re proud AQWA could support this important marine research that will contribute to the understanding and conservation of marine life.”
Collecting DNA from the water
Dr Bessey is a marine ecologist who invents different techniques for collecting environmental DNA (eDNA), which is DNA shed into the environment by plants and animals. Collecting and sequencing eDNA can reveal the presence or absence of a species.
“At first, people working with eDNA filtered it from many litres of water using pumps, which was slow and required access to a power source,” Dr Bessey said.
“Our idea was to make marine monitoring faster, cheaper and possible in remote places by developing membranes that could be submerged in seawater to collect eDNA passively.”
Dr Bessey tested her idea in the mesocosm at AQWA, submerging nine different membranes attached to an oyster frame and analysing the material that stuck to them.
Surprisingly, she found useful amounts of eDNA could be collected in just five minutes and there was little difference between using materials as diverse as hemp, synthetic sponge and filter paper.
“The work at AQWA opens the door to collecting eDNA from remote marine environments and using it to monitor entire ecosystems,” Dr Bessey said.
Counting fish without looking
Dr Power develops ways to collect and analyse whole cells that are shed by fish into seawater.
“I use techniques that are normally used to sort blood cells in medical diagnostics. My experiments at AQWA showed that we can use these techniques to sort fish cells from seawater and we validated this by using DNA sequencing to match the cells to the species present in the mesocosm,” Dr Power said.
“This new technique means people will be able to use a bucket of seawater to sample fish for genetic studies, instead of needing to catch individual fish.
“Importantly, we’ll be able to count the fish present in a location by using DNA to distinguish between individuals. This is important when monitoring an endangered species or assessing stock levels of a fished species.”
Dr Bruce Deagle from CSIRO’s Australian National Fish Collection uses eDNA to monitor the marine environment.
“Being able to efficiently capture eDNA from fish and other marine species is in seawater – and also capturing the rich information in whole cells – are key steps that will engage more people working in conservation and fisheries management,” Bruce said.
“Testing this technology in a mesocosm bridges the gap between the doing controlled experiments in a lab and real life science out at sea. It’s needed to transform new technologies into a frontline tools for conservation."