A combination of citizen science and artificial intelligence has been used to prove different populations of the weedy or common seadragon found across their range on the Great Southern Reef are genetically linked.

The discovery was made by participants in SeadragonSearch, a collaborative research project aimed at improving the understanding of seadragon populations through meaningful community involvement. 

The findings have quashed earlier theories that there were two subspecies of the marine animal.

Seadragons are unique to Australia and are found around the coastline from Geraldton in Western Australia through to Tasmania, with their distribution stretching as for north as Port Stephens in New South Wales.

The weedy seadragon is a type of fish found only in waters off the southern half of Australia.()

Co-founding researcher of the SeadragonSearch project Nerida Wilson said the project began by monitoring the ecology of seadragons and also looked at how different populations of seadragons were connected.

“We know in periods in the past, the sea level has been lower than it was and we know that Tasmania was connected to the mainland thousands of years ago, so we know seadragons couldn’t have lived there at that time,” she said.  

“So there’s been some suggestion that perhaps, on one side of that break is one subspecies of seadragon and on the other side might be another. 

“But what our genetics work has shown is that there is actually gene flow moving across that old barrier, and so we should consider them to be a single species across that Great Southern Reef.”

Facial recognition technology in use

Hundreds of scuba divers contributed photos of the animals as part of the SeadragonSearch project.

Weedy seadragons are found in water that is between 2 to 30 metres deep. By using the unique spot patterns found on their faces and bodies, researchers were able to distinguish between different individuals, while a machine learning program helped build up a timeline for each animal.

“We wanted to make sure, if we took a little tissue sample from an animal, we didn’t want to do it again and so we needed a way to differentiate between the individual,” Dr Wilson said.

“So it’s like that facial recognition, which people don’t like very much sometimes but in this case, it’s used for good.

“And so by putting images into the system, it can say, ‘oh, it links with this photograph taken at a different time point’, so we can build up a timeline for individual seadragons, which is amazing

A weedy seadragon at Flinders Pier on Victoria’s Mornington Peninsula.()

Describing seadragons as “a little like a seahorse tipped forward, with tendrils and appendages that look like algae”, Dr Wilson said the weedy seadragon was browny-reddish with tiny yellow dots all over. 

Dr Wilson said scuba divers loved the fish’s charismatic nature and many travelled from overseas for a chance to see them.

A common seadragon hides in a kelp forest.()

“So they’re almost as iconic as a koala for our marine systems,” Dr Wilson said.

“Someone described to me the other day that they just think they’re addictive and so as soon as someone sees one, they want to see another one and another one.”

Tiny fish expert in camouflage

“When these divers are looking for them, I always say make sure you have your camera settings ready because if you see one, and then look away for a second, it’s like they’ve vanished.

“It’s absolutely incredible. They’re still there, your brain knows that they’re there, but your eyes cannot find them.

“It’s astonishing and it doesn’t matter how experienced you are, it happens all the time.”

Dr Wilson said the genetic findings would have implications for protecting the species.

Weedy seadragons are unique to Australia.()

“Those animals on the east coast and then on the outside of the west coast have low genetic diversity and they’re also in the areas that are most likely to be first impacted by climate change, so it does mean that we probably need to monitor to them a lot more closely than we are.

“They may not have the ability to adapt to new conditions and so we need to pay special attention in this respect.”

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