As a young research assistant more than 30 years ago, Professor Mark Kennard joined Professor Brad Pusey in Far North Queensland to explore the humid, dense and remote catchments of the Bloomfield River.
The purpose of this 1993 fieldwork was to survey the little-known Bloomfield River fish fauna as part of a larger study of the freshwater fish diversity of the Wet Tropics of Queensland, following its declaration as a World Heritage Area in 1988.
What they ended up discovering during this rugged mission was entirely unforeseen.
“It’s not every day you get to uncover a new species, but Brad and I did just that on this trip more than three decades ago,” said Professor Kennard, who is now Deputy Director of Griffith University’s Australian Rivers Institute.
“We camped every night for three rainy months to sample most rivers of the Wet Tropics.
“That’s when we collected this little fish with a blue-green tinge that we hadn’t seen before; we didn’t know what it was, it didn’t ‘key out’ in a taxonomic sense.
“Once we got a preserved sample back to the lab and analysed it, we knew it was a new species, which is really exciting as a scientist.”
Introducing the Bloomfield River cod
Scientifically named Guyu wujalwujalensis by Professors Kennard and Pusey in recognition of the region’s Traditional Owners, the Kuku-Yalanji Aboriginal people and nearby Wujal Wujal community on the Bloomfield River, the Bloomfield River cod is one of Australia’s rarest and most geographically isolated freshwater fish.
From the team’s previous survey work, the species is currently found only within a small section of the Bloomfield River channel and some tributary streams, and is the only tropical representative of its family, 1,500km north of its nearest relative.
“But there is still so much we don’t know about it,” said Professor Pusey, now an Adjunct researcher at the Australian Rivers Institute.
“From a sample of 10 individuals, we know what it ate – that’s about it. We need to learn more about their ecology, distribution, reproduction and genetics.
“We need to know these things to better understand and manage the impacts of invasive species and of floods.
“We’re now getting a better idea of their habitat requirements, such as the large, tumbled rock slabs they like to dwell within.
“But that’s not a lot to know about a little fish, and certainly not a lot at present to ensure its continued survival.”
Humble beginnings to multi-partner project
Now, with a renewed focus on managing the Wet Tropics of Queensland, the Bloomfield River cod research project is supported by the Australian Government through the National Environmental Science Program (Resilient Landscapes Hub) and through the jointly funded Commonwealth-State Disaster Recovery Funding Arrangements.
The collaborative project, led by Professor Kennard of Griffith University in partnership with Jabalbina Yalanji Aboriginal Corporation and stakeholders, aims to inform management and conservation of this rare and threatened fish species, and manage these threats through science and Traditional Owner knowledge.
With key collaborators including the Queensland Government Department of Environment, Tourism, Science and Innovation; Terrain Natural Resource Management, Wet Tropics Management Authority, the Eastern Kuku-Yalanji people (Jabalbina Yalanji Aboriginal Corporation), and researchers from James Cook University, the Griffith University team mounted further explorations this year to answer remaining questions about the Bloomfield River cod, and what modern risks could impact its long-term survival.
Bobby Kulka, Eastern Kuku-Yalanji Traditional Owner, said working with the scientific research team and project partners had been vital to supporting two-way learning between traditional custodians and scientists, and increase awareness within their communities and skills to care for the species.
“We had no notion of the species until we started working with the research team,” Mr Kulka said.
“It’s been really important, now that we know they’re here and that they’re thriving, we can take that knowledge down to the younger generation and into the schools.
“This is our fish, and we need to take care of them, look after the ecosystem, and be proud of the work that’s going on.
“We all learn so much from each other and it’s vital for the species; they’ve been here for a long time and we want them to be here for a long time.”
Why is this little cod special?
The Bloomfield River cod is isolated to the river between the downstream Bloomfield Falls and the upstream Roaring Meg Falls.
As such, it has one of the most geographically limited distributions of any of the region’s freshwater fishes.
It is thought to be a relict species and may date back to the early Miocene around 20 million years ago.
It could represent what remains of a previously more widespread fauna that is now confined to temperate and sub-tropical regions.
However, recent threats, including the introduction of non-native fish and extreme flood events (such as Tropical Cyclone Jasper in 2023), are putting the species at risk.
Professor Kennard said its population was highly vulnerable due to its isolation, likely low genetic diversity, and potential inability to cope with introduced species or extreme events.
“It’s a relict, ancient population that’s never had to deal with more modern threats coming into the catchments,” he said.
“So, we need better knowledge to help us understand what we can do to maintain this unique species into the future, and working with the Jabalbina Yalanji Indigenous Rangers is a wonderful way to help achieve that.”
Into the wild with new technology
From multiple sampling trips in recent years, the research team has now surveyed more locations throughout the Bloomfield River catchment, finding the cod in previously unexplored stream sites thanks to the guidance of the Jabalbina Rangers team in Wujal Wujal.
When Professors Pusey and Kennard first discovered the cod during their 1993 fieldwork, surveying sites and sampling was much more challenging without the use of modern technologies routinely used today.
In those days, the team relied on paper topographic maps for navigation and sampled the fish with a bucket, nets and a very heavy backpack electric fishing device.
“When Brad and I did this 30 years ago, it was just the two of us in a vehicle – we were probably lucky to make it back out,” Professor Kennard said.
“This kind of science is not possible without our team of collaborators and our Jabalbina Rangers team.
“We’re working in quite a remote part of northern Australia on their country; it’s a long drive in, but it wouldn’t be possible to explore these beautiful creeks, rainforests and eucalypt forests without these teams behind us.”
During their most recent fieldwork, the research team from both Griffith and JCU employed the use of electrofishing, underwater cameras and snorkelling, drones and environmental DNA sampling to determine the distribution and abundance of fish species in the river.
They also recorded data on water quality and habitat conditions, and collected samples of the Bloomfield River cod and its food sources for later laboratory analysis.
“The damaging effects of extreme floods associated with Tropical Cyclone Jasper were clearly evident, with significant damage to riverbank vegetation,” Professor Kennard said.
The stream channel had also been greatly scoured with a substantial loss of submerged wood, leading to a significant change in fish habitat structure.”
Compounded with the storm’s wake, the presence of three new introduced fish species posed an increasing threat.
Two of these species – Tully grunter (Hephaestus tulliensis) and eel-tailed catfish (Tandanus tropicanus), were native to other rivers of the Wet Tropics region, and the guppy (Poecilia reticulata) – had been introduced from overseas.
“It is unknown how, why or when these species were introduced into the Bloomfield River, but all three are now very widespread and abundant,” Professor Kennard said.
“There is therefore no doubt they pose a significant risk to the Bloomfield River cod, through competition for food and space, and the potential for predation on cod eggs and larvae.”
In the lab and beyond
With fish, water and potential food sources sampled, the next stage of the project is to find missing pieces of the Bloomfield River cod puzzle, including their genetic diversity and biology, adding exponentially to the limited knowledge of this little-known species.
“Working in the labs with our genetics colleagues at Griffith University, we’re hoping to be able to answer some of those questions – how many are there, what is their distribution, how genetically diverse is their population, how long do they live, when do they reproduce, what do they eat, what external factors impact them?” Professor Kennard said.
“Can we get some signals from its very interesting past by sampling its DNA in the present?”
Findings from these analyses being undertaken at both Griffith University and James Cook University are expected to be completed in 2026.
Professor Kennard hoped these outcomes would inform next steps for on-ground conservation management to ensure the persistence of the Bloomfield River cod well into the future.
In the interim, the research team is developing a bespoke monitoring method the Jabalbina Rangers can use to track the health of Bloomfield River cod populations and their critical habitats long after the project is finished, for “their own species in their own country”.
As to why the nation and the world should know and care about this unassuming, little fish tucked away in the Far North of Australia, Professor Pusey said the risk of losing yet another faunal species to human impacts was far too great to ignore.
“It’s a really significant part of the biodiversity of Australia, and it’s a significant part of the evolutionary history of the fauna; it’s from a southern family, it is surprising it’s up here given the current distribution of the other members of its family,” he said.
“Yes, it is only a little fish, but it’s important in its own right.
“I would liken it to say ‘why worry about tigers, or pandas’ – they’re big and charismatic, sure; but these little fish, even without the charismatic aspect for a lot of people, are equally deserving of protection.
“We shouldn’t be causing the loss of more species, simply because we subjectively place a higher value on them than others.
“So, there is a chance here to do something of really great value.”
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Mark Kennard
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