OzCast OzFish Unlimited

Join us on this episode of OzCast as we look beneath the surface at the often-overlooked realm of small-bodied threatened fish species in Australian waterways with Dr. Nick Whiterod, a seasoned marine ecologist with over twenty years of dedicated research and conservation efforts. 
Dr. Nick Whiterod holds a PhD from Charles Sturt University, assessing the bioenergetic implications of large impoundments on Murray cod. His career has been marked by a profound commitment to the conservation of Australia’s freshwater ecosystems, particularly focusing on small-bodied fish and crayfish species. His work extends beyond mere research; he has played a pivotal role in the national conservation listing of more than 50 freshwater species.
Dr. Whiterod’s expertise is not limited to conservation alone; he is widely recognised for his skill in species reintroduction and managing complex ecosystems. His approaches and methods in reintroducing species to their native habitats have contributed significantly to the recovery of threatened species like the Southern Purple Spotted Gudgeon, Southern Pygmy Perch, Yarra Pygmy Perch, and Murray Hardyhead.
During the podcast, Nick explains the role these species have as vital indicators of ecosystem health and the concerning implications of their decline. The conversation extends to how the restoration of these fish populations can benefit the basin’s overall health, and what their presence, or absence, reveals about water quality and environmental management.
A focus of the discussion is the rediscovery of certain fish species in the Murray-Darling Basin, particularly the Southern Purple Spotted Gudgeon. Dr. Whiterod shares how these species, once common, have become rare in certain areas, with occasional surprising reappearances. The impact of habitat changes due to events like the Millennium drought and human efforts in conservation, including captive breeding and reintroduction, are examined. He also touches on the intriguing presence of northern fish species, like Barramundi, in southern waterways, raising questions about their survival and adaptation in unfamiliar habitats.
In looking to the future, the podcast delves into the threats posed by introduced species on native fish populations, focusing on the predatory habits of Redfin Perch and Trout. Dr. Whiterod discusses the threat to native species such as the Purple Spotted Gudgeon and Pygmy Perch, their dwindling numbers, and the factors contributing to their decline, which includes habitat destruction and disease. 

Throughout the episode, Nick provides an insight into the work he has completed in this area, speaking on the importance of maintaining ‘insurance populations’ to safeguard against potential losses down the track. Emphasising the importance of local conservation efforts, Dr. Whiterod underscores the role of individuals and community groups in protecting vulnerable populations, encouraging listeners to support threatened species in their local waterways. 
An underlying theme in the interview is the bridging of the gap between scientific research and community involvement. Dr. Whiterod stresses the importance of translating scientific knowledge into actionable strategies that individuals and communities can undertake. He emphasises that conservation is not just the responsibility of scientists and policymakers but is a collective effort that requires widespread community engagement.
Dr. Whiterod expresses cautious optimism about the future of Australia’s aquatic ecosystems. He acknowledges the challenges posed by climate change and habitat loss, but remains hopeful due to increasing awareness and ongoing conservation efforts. His message underscores the importance of continued research, public education, and dedicated conservation actions to protect these vital ecosystems.

In this episode of OzCast, fisheries scientist Craig Boys dives beneath the surface of the Hexham Swamp, a Ramsar-listed wetland with ecological and cultural significance. Craig highlights the intricate relationship between aquatic ecosystems and human interventions, particularly focusing on the impact of floodgates installed for flood mitigation. 

Throughout the episode, we explore the consequential shifts in fish and prawn populations, the resurgence of native species, and the broader implications for fishery productivity.  This episode is not only an educational journey through the swamp’s history and transformation but also a celebration of community involvement in environmental stewardship.  
Hailing from New South Wales, Australia, Dr Craig Boys is a Principal Research Scientist for the NSW Department of Primary Industries (Fisheries). Craig brings an extensive 20-year career to the forefront of fish ecology and fisheries conservation. His expertise is not only recognised nationally but also holds international acclaim. Craig’s academic journey includes a position as an Adjunct Associate Professor of Research at Charles Sturt University. His research portfolio spans across continents, including Australia, Southeast Asia, Europe, and America, demonstrating his global impact in the field. A leader in screening technology, Craig has dedicated his career to bridging the gap between primary industries and fisheries outcomes. 

Throughout the episode, Craig dives beneath the surface on the significance of Hexham Swamp. Once thriving with biodiversity, the installation of floodgates in the 1970s drastically altered the swamps ecological balance. Craig explains how these gates, designed to protect urban developments, inadvertently stifled the wetland’s ecological heartbeat by disrupting the natural flow of water. His insights offer a compelling story about the intersection of human intervention and natural ecosystems, emphasising the impact of seemingly minor infrastructural changes on waterway health. 

The floodgates led to decreased water quality, acidification, and a significant drop in aquatic life. These changes not only impacted the immediate area but also had cascading effects on the broader ecosystem, including local fish productivity. The swamp’s transformation from a vibrant wetland to a near-barren landscape starkly illustrated the unintended consequences of human interference in natural systems. 

A turning point in Hexham Swamp’s story came through advocacy, particularly by local commercial fisher, Jeff Hyde. Craig’s recount of Jeff’s relentless efforts to reopen the floodgates is a testament to the power of individual voices in driving change. Change was slow but steady. The gradual reopening of the gates marked the beginning of the swamp’s recovery, with notable improvements in water quality, fish, and prawn populations. 

Craig’s team meticulously tracked the ecological changes post the reopening of the gates. Their research employed a comprehensive approach, comparing the changes in Hexham Swamp to similar ecosystems, both with and without floodgates. This method provided a clear evidence, underpinning the importance of scientific data in environmental decision-making. 

The success story of Hexham Swamp goes beyond its boundaries, the long-term environmental benefits, including the resurgence of native species and the recovery of vital habitats. This case serves as a crucial lesson in environmental stewardship, highlighting the potential for change when human interventions are thoughtfully managed. 

The Hexham Swamp story is one of hope and resilience, demonstrating that with informed decisions and community involvement, we can aid in the recovery and preservation of our natural environments. 

What's behind the horrifying phenomenon of fish kills in Australian inland waterways? Join us as we unearth the many fish kills that have taken place recently with Prof. Lee Baumgartner – the leading scientists who is involved in the government enquiry investigating the events. Throughout the episode, Lee sheds light on the environmental culprits behind these disasters, stressing the importance of responsible river management going forward. From dissecting blackwater events, hydrology, bacteria and algae, river infrastructure and flow, the ‘perfect storm’ that leads to a fish kill is discussed so you can better understand what is happening to our native fish throughout the Murray-Darling Basin.  
Prof. Lee Baumgartner 
Prof. Lee Baumgardner stands as a revered figure in the realm of applied research, best known for his groundbreaking contributions to the intricate interplay of food, water, and energy. His work is particularly pivotal in regions where water serves as a lifeline for sustenance and economic activities, playing a crucial role in irrigation and hydropower. Lee directs his focus to communities reliant on fish, a cornerstone of biodiversity, nutrition, and income. However, these aquatic populations face a dangerous decline due to extensive river development, prompting Lee's active involvement in government inquiries into fish kills. 
Lee Baumgardner is no stranger to the corridors of power, having contributed to parliamentary inquiries and been appointed to prime ministerial advisory panels. His outreach extends to international and national media, where he tirelessly promotes the cause of healthy rivers. A recipient of prestigious awards, including the NSW Crawford Medal, Lee holds a Ph.D. in applied ecology from the University of Canberra (2005). Having only recently completed his commitments on the government panel enquiring into the fish kills, Lee offers insight into how environmental enquiries work. The transparency, which is important for the rec fishing community gaining trust in our respective state fisheries managements, leads the discussion to looking below the surface at what actually happened in the 2018 and 2023 fish kills.
Collaborating with a diverse spectrum of professionals—engineers, functional ecologists, social scientists, policy experts, and water professionals—Lee addresses the multifaceted challenges confronting these communities. Passionate about nurturing healthy rivers, his mantra, "A healthy river is an economic and environmental engine," encapsulates the essence of his recent research and advocacy. 
Beyond the realms of science and advocacy, Lee reveals a more personal facet—a passionate fisherman with a love for Port Phillip and Corio Bay. Whether chasing snapper, whiting, or flathead, he finds solace in the waters, embodying a harmonious connection between his professional pursuits and personal pleasures. 
Understanding Fish Kills  
Fish kills are complicated. Understanding them requires dissection of blackwater events, hydrology, stratification, bacteria and algae, river infrastructure and flow. Interestingly, both the 2018 and 2023 events were caused from different catalysts. As Lee explains on the episode, both fish kills were due to a lack of oxygen, yet how we came to that was due to different preceding weather events.  
In looking beneath the surface at these ‘environmental culprits’, Lee dives into the science behind blackwater events and breaks down this complex phenomenon. He explains how these occurrences, exacerbated by specific environmental conditions such as flood and drought, lead to drastic reductions in water quality and oxygen levels, culminating in mass fish deaths.  
Importantly, Lee highlights that blackwater alone is not the culprit for fish kills. A key component in this story is the process of stratification – the turning of water in a weir pool. As explained by Lee, the water at weir 32 in Menindee throughout 2018 and 20

On this episode of OzCast, Dr Martin Mallen-Cooper re-joins the show to look below the surface at one of the most topical questions circulating our inland fishing communities – should Australia release the Carp herpes virus (cyprinid herpesvirus 3)?  

Martin, who has spent decades looking into the health of our freshwater rivers in Australia, sets the record straight on how the carp virus would work if released and offers his expert opinion on which direction the Australian government should take.

Dr Martin Mallen-Cooper is a highly respected river ecologist. He was born in 1958, in Sydney and grew up with a strong love for the ocean, rivers, and fishing, which led him to pursue a career in aquatic sciences. Dr Mallen-Cooper received his undergraduate degree in Environmental Science from the University of Technology Sydney in 1980, where he developed a passion for freshwater ecosystems. He worked as an environmental consultant and then joined NSW Fisheries in 1984 to research the design of fishways (structures to get migratory fish past dams and weirs), which became the subject of his PhD.  

Martin is the first to concede that no freshwater fish ecologist in Australia can actively study the health and solutions for our native fish, without understanding the detrimental effect European carp have. First brought to Australia in the late 1800s, Carp cause their main environmental impacts through their feeding habits. As adults, they usually feed on the bottom of rivers and ponds. They feed by sucking soft sediment into their mouths, where food items are separated and retained, and the sediments are ejected back into the water.  

Martin explains that when carp are present in high densities, the resultant suspended sediment can bring on more problems, including deterioration of water quality and increased nutrient levels, reduced light penetration resulting in reduced plant growth, invertebrates and fish eggs and clogging of gills of other fish species.  Carp feeding can result in fewer aquatic plants: carp will graze on plants directly and uproot plants during feeding and are also effective grazers of surface films on plants and rocks. 

Throughout the episode, Martin explains that various bio-control mechanisms have been implemented over the decades, with limited success – which has led Australia to now consider a more extreme measure in the Carp herpes virus.  In breaking down how the virus would work; Martin distils a common misconception about introducing viruses in aquatic environments. He explains that the virus would effectively ‘knock down’ carp numbers for a short period, which would allow native fish numbers to survive. After this period, the carp numbers would bounce back, with native fish having a stronger foothold in the environment allowing them to compete with the carp. Martin believes Australia would have a 3–5-year window to act on a number of issues to see this virus work effectively.  

When asked whether a virus like this should be a concern for native species in the river, like Murray Cod and Golden Perch, Martin explained the virus is already naturally occurring in carp around the world and only impacts carp  

An important issue to consider, according to Martin, is the control mechanisms for the dead carp which would inundate our river systems in the years preceding the release of the virus. Just as we experienced with the Menindee fish kills in 2018 and 2023, dead fish raise community concerns around water quality, drinking suitability and aesthetics of our rivers and towns.  Dealing with the dead fish is an important cog in deciding whether the virus is released - but overall the science looks positive.  

In an interesting development, Martin uncovers the notion that the carp virus might very well get to Australian rivers anyway, through natural causes or through it being unintendedly introduced. In Martin's opinion, Australia needs to be r

In this episode of OzCast, Jason Tanner dives beneath the surface of South Australian waters to unveil how he is working to “green the blue” by dropping sandbags in strategic areas to bring back the lost seagrass meadows of yesteryear. After spending over 25 years developing this technique from the ground up, he explains how his work went from an idea to a now industrial-level program that sees tens of thousands of bags being deployed every year.  

Jason has 30 years’ experience overall in marine ecology, working in tropical and temperate systems. He has published over 80 papers, most in high-profile international journals, and numerous reports. He undertakes field and laboratory studies of marine ecosystems and also has a strong grounding in statistics and mathematical modelling. 

His first exposure to seagrass was as a teenager snorkelling in the coastal lakes of southern NSW, although it would be many years before he would return to them, taking a detour via the coral reefs of the Great Barrier Reef in between.   

This detour involved a PhD and postdoctoral studies on corals at Heron Island, before moving to the South Australian Research and Development Institute to study the impacts of prawn trawling on the seafloor.  From here he became interested in the way fragmentation of seagrass habitats influenced the fauna that lived in them, which then progressed to an interest in the seagrasses themselves and how to reverse the extensive habitat loss seen along the Adelaide coast (and elsewhere).  

Throughout the episode, Jason explains that this interest led him to develop novel low-cost techniques for seagrass restoration tailored to the main species found in South Australia.  His hessian sandbag technique can be deployed for 5-10% of the cost of traditional transplantation involving divers and doesn’t require the removal of seagrass from a donor meadow.   

Instead, it relies on providing a firm substrate for naturally present seedlings to attach to (for wireweed - Amphibolis) or collecting beachcast fruits that would otherwise dehydrate and be lost (for strapweed – Posidonia australis).  He is now in the process of establishing a 20-hectare restoration plot just north of Adelaide, funded by the Commonwealth Government, which will be the largest single seagrass restoration in Australia.  

Jason offers a wealth of information on how programs like this develop and transform, to the point where he is now dropping over 25,000 bags in a single deployment. 

 Having spent countless hours researching seagrass, Jason highlights the impacts that seagrass has faced on the South Australia metropolitan coastline. Over the last half-century or so, more than 6,000 hectares of seagrass has been lost off the Adelaide coast due to anthropogenic nutrient and sediment inputs.  This loss has led to coastal erosion, decreased habitat, loss of carbon storage and decreased fish abundance.  Recent improvements to wastewater treatment and stormwater runoff have led to some natural recovery, but changes in sand movement resulting from the loss now prevent the recolonization of many areas. 

While the hessian bag method has resulted in the successful establishment of small patches of seagrasses that have persisted for around a decade, and which are now functioning like natural patches due to colonisation by other marine plants and animals, the development of the technique has not been straightforward.  Throughout the episode, Jason unveils how he has had to refine the technique over the years when it comes to developing of a good understanding of the timing of recruitment, and methods to ensure the maximum number of bags are dropped in a given season.  
Jason explains that the sandbags provide a stable environment that overcomes sand movement and allows the seedlings to establish, before the bags rot away. Without the bags, seedlings don’t have much to attach to, and any that do settl

PART 2:
In this episode of OzCast, Professor Kendrick unveils the crucial role that seagrass plays in marine and terrestrial ecosystems, shedding light on its remarkable ability to support marine life and store blue carbon, even more effectively than tropical rainforests. With over 40 years of professional experience in the restoration of these marine ecosystems, Professor Kendrick dives beneath the surface on all the trials and tribulations of bringing these lost meadows back to their former glory – from small-scale projects, all the way to industry-leading community-led projects like Seeds For Snapper.  

Professor Gary Kendrick is a leading marine ecologist in the areas of marine benthic biodiversity, resource mapping, seagrass and seaweed ecology and seagrass restoration. He has worked with government and industry to determine needs and develop solutions for climate change threats as well as environmental and conservation issues in Australia’s exclusive economic zone.   

He has successfully led numerous interdisciplinary teams to address gaps in our knowledge by mapping benthic resources in the shallow continental shelf around Australia and in studying the environmental impacts on seagrasses and seaweeds of commercial fishing, oil and gas infrastructure, dredging, coastal development, coastal eutrophication and desalination outfalls.   

Throughout the podcast, Gary discusses the idea of awareness: of not just when seagrass was recognised as being lost in Australia, but the awareness of how important it is to both animals and humans. He provides anecdotes on the types of ways we used seagrass, which ultimately led to its decline over the last 240 years. According to Gary, we are losing one football field of seagrass every 30 minutes, globally.  

Drawing from his extensive travels, he compares Australia's efforts on the international stage, giving us a comprehensive overview of where we stand globally in seagrass preservation. He explores the major international policies that have shaped seagrass protection in Australia, highlighting the ongoing work needed to secure seagrass ecosystems in international law. 

His seagrass restoration work previously focused on technical solutions and developments to improve the restoration success of seagrasses. More recently, however, his emphasis has shifted to working with the community to develop restoration at larger scales. He presently works on supporting the large OzFish community program, Seeds for Snapper, which is a collaboration with the University of Western Australia that is scaling up seagrass restoration from 100m2 to hectares using seeds of the seagrass Posidonia australis.  

Professor Kendrick emphasises the power of community involvement in seagrass restoration. Learn why he believes that programs like "Seeds For Snapper" are not just for experts but something everyone should engage in, emphasising the collective responsibility we all share in preserving these invaluable ecosystems. 

With years spent swimming amid these submerged meadows, Gary shares how he endeavours to quantify the value of a square meter of seagrass, unveiling a surprising truth that challenges our preconceptions. He delves into the methods that work and those that don't. It’s a percentage game and he explains why restoring even 10% of seagrass seeds is a monumental achievement in the world of conservation.  

Gary’s long-term research goal is to develop a predictive framework for understanding the spatial and temporal dynamics between marine species distributions, their biology and the physical environment. His work on this has identified appropriate descriptors of extensive historical losses of seagrass habitat due to human impacts and modelled emergent landscape-scale phenomena related to the clonal growth of seagrasses at the shoot scale and the evolution of seagrass landscapes. This line of research has led him to question our understanding of