It is one of the world’s great migrations, yet it is usually unseen. Under the cover of darkness, eels slip into the ocean to then travel thousands of kilometres to breed. But where do they go?
Each summer, at the new moon when the sky is at its darkest, eels along Victoria’s coastline start disappearing into the ocean.
After living in fresh water for decades, they are returning to the place they were born.
They can even travel short distances over land to reach a waterway that will carry them out to sea.
This distant migration confused the eel-curious for centuries and led to some bizarre theories about where they come from — Aristotle thought eels spontaneously generated.
Even though science has come a long way, much about eels remains a mystery.
For the first time, Australian scientists are tracking eels with satellites to understand their migration.
The study is being undertaken by the Victorian government’s Arthur Rylah Institute for Environmental Research.
As the sun sets on Port Phillip Bay, Wayne Koster lays out long cylindrical nets at the mouth of a creek.
Tonight, his team hopes to catch migrating eels large enough to carry the satellite transmitters.
Since 2019 when the study began, 20 transmitters have been attached to eels, with each device costing thousands of dollars.
Sometimes it can feel like leaving a message in a bottle to the mercy of the ocean.
The researchers hope the eels will make it far enough to gain useful data; they also hope the devices successfully transmit.
Yet one of the best data records to date was retrieved by accident.
“That tag had actually failed to transmit. It had been eaten by a whale and the antenna was damaged,” Dr Koster says.
“Fortunately, someone who was fossicking along a beach [on Lizard Island] found it and sent it back.”
Normally, after the device is attached to an eel it collects and stores data for the next six months as the eels swim to their spawning grounds.
“Then [the device] pops up to the surface and transmits to the satellite network,” Dr Koster says.
“We are then able to retain that data and reconstruct migratory tracks of where the eels have been.”
The transmitter resurfaces because by then the eel is dead — the migration to the breeding grounds is the culmination of a life’s journey.
After breeding, the eels, which can reach the age of 50 or more, die.
There are two species of Anguillid eels in Victoria — short-finned and long-finned eels.
Sometimes the scientists venture out to catch them for several nights before they find an eel large enough to carry a device.
It is cold, wet work, undertaken in the middle of the night when the eels are most active.
But the scientists’ dedication is paying off.
“We’ve tracked eels from the west coast of Victoria for about 3,000 kilometres up to warm tropical waters around New Caledonia, an area around the Coral Sea,” Dr Koster says.
This is the first time the oceanic migrations of Australian eels have been tracked and documented, he says.
Similar research has been undertaken to track eel migrations from North America and Europe to the Sargasso Sea in the North Atlantic.
Over the past 50 years, eel populations in the Northern Hemisphere have substantially declined.
“Overseas, many species are now listed as threatened or endangered,” Dr Koster says, “so understanding fundamental aspects of their life history, like their migration patterns, is a really important element in ensuring Australian populations don’t follow a similar fate.”
Welcome to eel country
In western Victoria, the scientists are collaborating with Gunditjmara traditional owners to discover what prompts eels to move out of fresh water and begin their migration.
The relationship between Gunditjmara people and eels can be traced back thousands of years through the ancient stone eel traps that weave through a lush swampy landscape known as Budj Bim.
These are some of the oldest known fish traps in the world, dated to more than 6,000 years.
The Gunditjmara people who constructed them created a complex aquaculture system.
“The systems were designed to operate at various times of the year as water levels rose and fell,” Gunditjmara man and Budj Bim project manager Denis Rose says.
It meant the Gunditjmara had a reliable source of eel — or kooyang — for much of the year which they also smoked and traded.
Mr Rose spent his youth around these wetlands catching eels, a place which many Gunditjmara people have fought never to be separated from.
He can reel off different ways to catch an eel.
“Bobbing, netting, just a hook and some bait.
“I knew how to cook eel a few different ways, how to prepare them — I used to think for many years that I knew a heck of a lot about eels.”
But in the years since the Gunditj Mirring Traditional Owners Aboriginal Corporation employed an eel biologist, and now through this current research, Mr Rose says he continues to learn about their complex life cycle.
He says there are many pressures on eels, from climate change to drainage of wetlands and commercial fishing.
“We’re getting some better information about their life cycle and hopefully to assist in the protection and the continuing supply of young eels.”
Using acoustic transmitters, Dr Koster’s team has been tracking eels through the Budj Bim waters.
“What our research shows is eel migrations in fresh water are often linked to changes in water level, changes in river flows,” he says.
For Gunditjmara people, seasonal indicators let them know when the eels are beginning their migration.
“When the acacias start to flower, we call that kooyang time, because that’s when the eels are on the move,” Gunditjmara ranger and land manager Ben Church says.
The research will build on traditional knowledge and help inform how water flows can be managed through the Budj Bim wetlands.
“It informs us for future management, not only of the kooyang, the eels, but also its habitat,” Mr Church says.
Managing the eels’ habitat will in turn protect other species.
“It’s not always about one species for us,” he says.
“It’s about the whole country and caring for country as equal.”
As Mr Church finishes saying this, a crow flies by low and fast and lets out a definitive caw.
The ranger looks up and chuckles.
In 2019, Budj Bim gained UNESCO World Heritage status due to the cultural and historical importance of the stone eel aquaculture sites.
This area is eel country. The land is dotted with reminders of their presence and importance.
Not far from Budj Bim, further inland at Lake Bolac, an ancient stone eel sculpture was recently destroyed by a farmer.
“We’re in the process of building an eel aquaculture facility — essentially a visitor centre at Tae Rak (Lake Condah) to show the story of the eel,” Mr Rose says.
“To highlight the importance of why we should be looking after eels and why we should be improving their habitat.”
One of the key findings from the research so far reveals how migrating eels play a role as a food source.
“Sharks and whales are eating the eels off the Australian coast,” Dr Koster says.
It is possible to know if an eel is eaten, he says, because there is a sudden jump in temperature recorded in the data.
“Potentially changes in the numbers of those marine predators like whales and sharks might influence [eel] populations.”
The research is also considering how human activities such as offshore energy developments and climate change could impact migrating eels.
On their way to the spawning ground, eels swim against the East Australian Current.
“That current is projected to strengthen and push further south under climate change,” Dr Koster says.
“So, in years with a stronger southward flow, potentially it will take eels longer to reach those spawning grounds.
“Or fewer eels might actually make it there, which has implications for spawning and recruitment success.”
For eel fisherman Zac Taylor, water is the essential element both to the health of eels and his business.
A second-generation eel fisherman, Mr Taylor lays his nets in the winding rivers near the Twelve Apostles.
The eel migration is the high point of the wild eel fishing season.
“That’s where I make most of my money,” he says.
Mr Taylor supplies an exporter who sells eels to several Asian countries where they are a delicacy as well as supplying some local fish markets.
He also sells juvenile eels to fishermen with licences to fatten them up in lakes; it is what is called stock-enhanced fishing.
“The industry is based on us catching little eels out of the rivers and supplying the lakes inland to grow out.
“Down here they’ll take 20 years to grow into a sizeable fish, whereas up there they can turn them over in about four to five years.”
But the millennium drought wreaked havoc on Victoria’s commercial eel industry. It is why Mr Taylor is also a plumber.
“That’s why my dad made me go and get a trade, something to fall back on, which he didn’t have during the drought and it was pretty hard times.
“If you don’t get floods, you don’t get eels. It’s as simple as that.
“The little ones have got to come upstream, and the big ones have got to come down, so if you don’t get floods it won’t happen.”
But Mr Taylor says he is confident there are enough rivers and lakes closed to licensed fishermen to ensure the population is maintained.
Unlike some other popular eating fish, eels cannot be bred in captivity for commercial production because their life cycle is so complex.
Scientists in Asia and Europe, however, continue to develop the means.
But former scientist turned eel exporter Lachlan McKinnon says he cannot see it happening in Australia.
“Actually, closing the life cycle for Australian species of eel, it’s not a big enough industry or big enough market to make that sort of investment,” he says.
Mr McKinnon believes a domestic and export industry based on wild catches is full of potential, but fisherman Graham Milner is less optimistic.
“I believe the Victorian eel fishery is doomed,” he says from his lounge room in Colac.
Surrounded by taxidermy deer, rabbits and ducks, Mr Milner spends more time working as a professional shooter (employed by Landcare groups to keep feral animal numbers down) than he does fishing eel.
Carp is the main problem, and water – the draining of wetlands or drought, he says.
“I believe that not in my lifetime, but in my son’s lifetime and the other young fishermen in the industry, in 40 or 50 years’ time they won’t have an export industry. Because of the carp.”
The cycle repeats
Eels are important to maintaining healthy waterways, Dr Koster says.
“They play a role as a predator in freshwater environments, so they can shape or influence aquatic ecosystems.”
But he says these slimy, serpentine creatures perhaps have not enjoyed the attention they deserve in Australia.
“I think being a bit snake-like, it does tend to put people off and as a result they have become an overlooked animal.
“We don’t have a precise estimate on the number of eels or the trends in their populations [in Victoria].
“There’s so many knowledge gaps, so we’re hoping to fill some and help contribute to the sustainability of their populations into the future.”
As the satellite-tracking project continues indefinitely and more knowledge about eels is documented, these mysterious creatures are a reminder that everything is connected.
Waterways, food chains, people.
What began as larvae drifting on ocean currents from spawning grounds in the Coral Sea, eventually washed into fresh water and transformed into a powerful muscular fish.
“After spawning, the adults die. The larvae then commence that journey back to the coast,” Dr Koster says.
“And the cycle repeats.”
Reporter: Rhiannon Stevens
Photography: Rhiannon Stevens
Video: Rhiannon Stevens and Peter Healy
Digital producer: Daniel Franklin