BACK TO NEWSCould a seahorse smaller than your finger still live in the ocean off the coast of Australia?
The Search for Lost Species is preparing for its first ever marine expedition
By Devin Murphy on October 09, 2024 
“They’re tiny. They’re miniscule,” says Christina Biggs, lost species officer for Re:wild, with a giant grin across her face.
She’s talking about the Bullneck Seahorse, a cryptic species that lives in deep ocean waters off the coast of Southeastern Australia. Fully-grown, the species is only about 55 millimeters (two inches) long. And even though the seahorse is tiny, it has attracted big curiosity from scientists.
“When I started going down this whole wormhole of trying to research the Bullneck Seahorse, there really is no information out there,” says Justine Gordon, a marine biologist with Oceanreef Aquaculture Australia.
Biggs and Gordon visited fishing communities in Australia in late April and May 2024 to try and begin to fill in some of that information gap.
An unusual seahorse
No scientist has ever seen a Bullneck Seahorse in the wild. They think the species lives on reefs or rocky areas, holding onto corals or seaweed with their long windy tails. But it’s hard to say for sure.
“There are only four specimens that have ever been seen, and they come from wildly different locations,” says Biggs. “When you look at the scope and the size of ocean territories, they're vastly, vastly far apart.”
The first specimen discovered by Western science was pulled up in a trawling net off the coast of Eden, a small town on Australia’s Sapphire Coast. The three other specimens were all found in different parts of the ocean with very different conditions at different times of the year—making it tricky to know where to start looking for the species.
The Bullneck Seahorse has been described as a “bizarre seahorse” with “unusual features” — namely it’s wide neck. Scientists think it may belong to a completely new genus (group of species) or potentially even be a species of pygmy pipehorse and not a true seahorse at all. But until they see one in the wild and learn more about it, all they can do is wonder.
A strong memory
Despite the questions scientists have about the Bullneck Seahorse, fishing communities and Indigenous communities in coastal Australia still remember the species. Biggs and Gordon spent 10 days visiting eight different communities along the coast from Melbourne to just south of Sydney, asking if anyone had seen the seahorse and if they could share any details about it. They visited bait-and-tackle stores, talked with retired and former commercial fishermen.
“We even went onto the docks as well and talked with people on boats who had just come in from fishing and had good conversations with them as well,” says Gordon. “We only found two individuals who seemed to think that they saw the seahorse back in the ‘80s.”
They estimate they talked with more than 100 people and those interviews helped point them toward a town in Victoria. Looking at photos and illustrations that Biggs and Gordon had comparing the Bullneck Seahorse to juvenile Potbelly Seahorses —a much more common species that lives in shallower waters— two fishermen were adamant that they had seen the seahorse decades ago. They said that seahorse had the defining characteristics of the Bullneck Seahorse— a thick neck and short snout.
“We ended up circling back to a place called Lakes Entrance, where a lot of the data was pointing with the people who would know the most about the Bullneck Seahorse,” says Biggs. “The first place we went was this fascinating and cool little place called The Shell Museum that has a collection of just fascinating stories about the ocean and the creatures within it— and beautiful visuals.”
The family-owned shop and museum has a deep knowledge of local marine species and may have even had a Bullneck Seahorse in the museum at one point. They knew exactly what species Biggs and Gordon were looking for and how to tell it apart from other seahorse species, but no one could remember seeing one recently.
“I did not expect that people would know and recognize this species because there is so little in the academic literature,” says Biggs. “It’s heartening that communities know about it and can describe it, and have seen it within their lifetimes. It’s been quite a while, but within lifetimes.”
Many stories about seeing Bullneck Seahorses had one thing in common: the type of boats they were pulled up on were Danish trawlers. Danish trawlers use very tight-woven nets with extremely small holes to bring up their catch.
“We tracked down the original boat that the holotype came up on in those nets,” says Biggs. “That was really interesting. Again, there’s just lots of generational families there who have continuous knowledge of how landscapes change and how species’ composition changes through their work over decades.”
Before interviewing communities Biggs and Gordon thought that the seahorse likely hadn’t been seen in almost 30 years because it lived in deep and inaccessible parts of the ocean that are difficult to reach because weather conditions usually don’t allow for it. Their thinking was that it probably wasn’t threatened, but instead has always been rare.
A similar species, the Ruby Seadragon, another deep-water species, had a similar story. Scientists had originally mistaken it for the Weedy Seadragon, but careful analysis proved it wasn’t. An expedition off of Western Australia using ROVs was able to find the species in the wild.
“I feel like if the Ruby Sea Dragon —being such a large species— has the same story, and then scientists found it as soon as they started looking for it, [the Bullneck Seahorse] just hasn’t been found because no one’s been looking for it,” says Gordon.
The new information Biggs and Gordon got from talking with fishers, divers and even tourism operators made them hopeful and gave them pause. It’s possible that the species hasn’t been seen because it lives in such deep water, but it also might be in trouble.
Lost in the ocean
Originally, Biggs and Gordon thought they would be focusing their search efforts in places where the Bullneck Seahorse had been previously seen. But there is another area that might be of interest. Cape Paterson, off the Southwest coast of Victoria, is on the edge of a scallop dredge area, and a research vessel once pulled up a Bullneck Seahorse in a trawl net there.
“What we really want to find out is what area has not been touched by commercial trawlers,” says Biggs. “We thought that we were looking for the data on where the sightings are, but really what we want is to find intact habitat without sightings, because that seems like the most likely place now where we might still be able to find the seahorse.”
The edge of the scallop dredge area is in slightly shallower water —a little over 260 feet deep (80 meters)— but it's still within the range of where the Bullneck Seahorse could live. And since dredging damages the ocean floor, the activity might have subsequently concentrated seahorse populations in shallower water.
But deciding where to look first will be no easy task and could take many different shapes. First, Biggs and Gordon will be compiling their dozens of data points and overlay them on a map of the seafloor and ocean currents.
“Looking for marine species is an entirely different category of difficulty for the Search for Lost Species,” says Biggs. “A lot of terrestrial searches, you can use binoculars, you can use camera traps. There’s a full suite of tools that’s been used for decades in that space that don’t exactly translate over to water environments, particularly this environment off the coast of Eden, Australia. It is rough, open seas. It’s barely been explored.”
When an expedition team does get in the water, they are not going to be able to just hop in the water and swim around looking for tiny seahorses. They will need specialized equipment, like underwater drones and baited remote underwater video systems (BRUVS). And all of that will have to be perfectly timed with the weather. It’s estimated that out of every 14 days, usually only two days will have calm enough weather to sail up to 16 kilometers offshore from Lakes Entrance.
eDNA kits and the samples they collect will be the most useful to any expedition team. If they detect any environmental DNA they’ll be able to focus their search efforts much more quickly. But first they’ll need a Bullneck Seahorse DNA sequence to compare any eDNA sequences to.
“We would really like to get a molecular sequence, a DNA sequence on one of the specimens, which has been notoriously difficult, “ says Biggs. “It’s fixed in formalin, which has been impossible to extract DNA from.”
The Colossal Foundation, a partner of Re:wild's, is supporting searches for Re:wild’s most wanted lost species, and may be able to deploy their state-of-the-art technology to collect DNA from one of the specimens.
Spreading the word
Although Biggs and Gordon have wrapped up the initial stages of the search, they got helpful information from local residents and fishers around Lakes Entrance. Oceanreef Aquaculture created a wanted poster with photos and a description of the species with Gordon’s contact information. Most people took a handful to keep and share with their friends and communities.
“I really do believe, ‘seek and you shall find,’” says Gordon. “If you don’t go looking for something—especially something that lives that deep— if you’ve got hope and you’ve got the will to go looking…I truly believe there’s no reason that it couldn’t be there.”
Biggs agrees.
“The Search for Lost Species is such a grand treasure hunt,” she says. “It’s always so surprising the twists and turns it takes, particularly of these very difficult cryptic creatures. I think I’ve always known this was going to be maybe the most difficult of all the most wanted lost species to find. I still feel that way.”
The search for Re:wild’s most wanted lost species is supported by the Colossal Foundation.
About the author
Devin Murphy
Devin Murphy is Re:wilds’s senior communications specialist and helps Re:wild and its partners tell stories about the work they do to protect wildlife and wildlands around the planet. Her favorite stories about conservation include fascinating and little-known species and the dedicated humans protecting them.
