Millions of rotting fish: turtles and crays can save us from Carpageddon

Ricky Spencer, Western Sydney University; Claudia Santori, University of Sydney; James Van Dyke, Western Sydney University, and Michael B. Thompson, University of Sydney

The Australian government plans to target invasive European carp with a herpes virus, leaving hundreds of thousands of tonnes of carp rotting in the river systems that supply our drinking water and irrigate the fruit and vegetables we eat. The Conversation

The aim of “Carpageddon” is to return Australian aquatic ecosystems to their pre-carp state by eliminating or reducing the serious pest species.

Carp currently make up 83% of the fish biomass in the Murray-Darling Basin in New South Wales. They alter river and lake habitats in a way that reduces habitability for native species, including five threatened species. They also have a major impact on inland fisheries, with an estimated annual economic cost of A$22 million.

This all makes a substantial argument for releasing a carp killing herpes virus. However, dealing with the aftermath could cost A$30 million for NSW alone.

Cleanup costs could be reduced by introducing viruses to discrete populations. However, if the virus escapes into the Murray-Darling Catchment, we will lose control of the virus spread and carp death will be rapid and widespread.

Without a dedicated cleanup effort, the sudden influx of millions of dead fish could permanently pollute our waterways. A potential solution is to recruit nature’s cleaners to do our work for us – scavengers like turtles and crayfish. They could save us from carcass-choked rivers and wetlands, but only if we can protect them from endangerment and extinction.

Turtles and crayfish are our unlikely saviours

Carp carcasses are normally eaten by scavengers, a process that’s vital to the food web (the system of what eats what in a given environment). In fact, the majority of dead fish are consumed by scavengers.

As such, simply removing the carp carcasses may reduce the overall amount of nutrients in the ecosystem. This would destabilise the food web, especially for scavengers such as turtles and crayfish who rely on them.

Instead, these scavenging species can provide crucial biocontrol. They would eat any decomposing flesh in our water systems, particularly in areas we can’t easily access with nets, boats and trucks. They would maintain the quality of our waterways in three ways:

  • Slow the spread of bacteria that break down dead fish, keeping water safe to drink and limiting deoxygenation that could devastate native fish species;

  • Digest carp directly into basic nutrients (fertiliser) that is more readily absorbed by plants and primary producers;

  • Semi-permanently store carp nutrients in their slow to decompose shells and exoskeletons, preventing or limiting toxic algal blooms caused by excess nutrients in water.

Our unlikely saviours are also dying

Threats to crayfish include agricultural and urban expansion, recreational fishing, pollution from surface runoff and insecticides, and introduced species such as trout and cane toads.

Consequently, native crayfish are declining, with nearly 80% of Spiny Crayfish recognised as threatened. However, yabbies have expanded their range.

Turtles on the other hand, are in sharp decline throughout the Murray Catchment and elsewhere in Australia. A recent gathering of turtle experts in Canberra discussed major threats to turtles, and ways to protect them.

The meeting addressed major causes behind the 2% annual mortality rate of adult turtles that is leading the species to rapid extinction. Cars and foxes kill a significant number of adult turtles every year, and foxes destroy more than 95% of turtle nests in the Murray-Darling Basin.

Changes to the hydrology of the Murray Catchment may also impact turtles. Some species require permanent wetlands, while others prefer to move between temporarily flooded wetlands and more permanent waters.

Following modern water management, some temporary wetlands are permanently flooded or gone and some permanent wetlands are dry.

All of these threats together may cause turtles to become functionally extinct in the near future, meaning they cannot play their significant role in the ecosystem anymore.

How can we help conserve the turtle population?

Such a sudden decimation of carp has potentially catastrophic consequences. But it may also be an excellent opportunity to recognise the importance of turtles and prioritise their conservation.

In a recent study, headstarting was named as the only management tool that could protect freshwater turtles from the multiple threats throughout their life cycle and eliminate all risks of extinction.

Headstarting involves rearing eggs or newborn animals in captivity, then releasing them into the wild. It has been controversial for decades, but releasing thousands of little turtles throughout the Murray River just might rescue us from the post-apocalyptic effects of Carpageddon.

Ricky Spencer, Associate Professor of Ecology, Western Sydney University; Claudia Santori, PhD candidate, University of Sydney; James Van Dyke, Postdoctoral fellow, Western Sydney University, and Michael B. Thompson, Professor in Zoology, University of Sydney

This article was originally published on The Conversation. Read the original article.

Stinking dead fish portend major problem with carp herpes release

Simon Chapman, University of Sydney

In April last year, this column looked at six concerns about the planned release of carp herpes virus (Cyprinid herpesvirus 3 or CyHV-3 – also known as koi herpesvirus, or the carp herpesvirus) into Australian rivers in an attempt to dramatically reduce the plague proportions of these introduced and destructive “river rabbits”. Radio JJJ also broadcast a special report in May on “what could possibly go wrong”.

In the eight months since, the NSW government has held public consultations with interested parties and the Australian government’s Department of Industry published a final report late last year.

This report concentrated on whether the virus might impact other fish and native species. It concluded:

Following clinical, molecular and histological observations, we now know that CyHV-3 does not infect (and therefore cannot affect) a wide taxonomic range of non-target animals including: 14 species of fish (13 native species, and the introduced rainbow trout); yabbies; a species of lamprey; two amphibian species; two reptile species; chickens; and mice. These results strongly suggest that both spillover infections and species jumps are highly unlikely with CyHV-3, and, therefore, the results encourage further work on the use of CyHV-3 as a potential biocontrol agent for carp in Australia.

The report also discusses a planned infected carp release into the Lachlan river catchment area in NSW. The Lachlan flows some 1,440km with its main stream and tributaries passing towns that include Cowra, Forbes, Condobolin, Lake Cargelligo, Hillston, Booligal, and Oxley.

Concerns about the release of CyHV-3 possibly affecting other aquatic species has been a major issue and these findings may provide some assurance of safety.

However, in my 2016 column, I noted the carp-deadly herpes virus had first “appeared” in Israel in 1998 and had since migrated to 33 nations through fish commerce. This seemingly innocuous “appeared” word, read in conjunction with the normal never-say-never, careful language of science in the government final report (“strongly suggest”, “highly unlikely”) raise questions about the provenance of the new virus before it first “appeared” in Israel.

If the 1998 appearance was a mutation of a previously benign virus, obvious questions arise about future mutations, including whether such changes might be capable of jumping species once the virus is released into NSW rivers.

The current situation appears to be full steam ahead with a gung-ho Barnaby Joyce publicly making statements about plans to start the release at the end of 2018. $15m has been budgeted for the exercise.

Mini “stench rehearsal” at Hindmarsh Island

This week, ABC News reported “hundreds” of dead carp had washed up on Hindmarsh Island near the sea in South Australia. Blackwater from decomposing vegetation washing into the Murray-Darling during the 2016 floods making its way downstream is seen as responsible for the fish kills. A local resident emphasised the stench. Her words were important and portend a major concern I raised in my column last year.

Catharina Taylor told the ABC the dead and rotting carp were causing a “horrible smell” and she feared the smell would get worse in the summer heat.

She had alerted both her local council and the South Australian State Government’s Primary Industries and Regions department about the problem, who offered no help: “Only thing that I actually heard is that they cannot help, they haven’t got the manpower and we should get the community behind us,” Ms Taylor told the ABC.

Photos in the ABC report show hundreds of dead fish on the shores of the island causing the stench. I have experienced the smell of a single dead carp. It is not an experience easily forgotten. No one has reliable figures about how many carp are in Australian waters, but estimates range from 2-6 million tonnes. The Hindmarsh Island experience will be like a splinter in the handrails of the Titanic compared to the problem the “carpageddon” we are being promised.

A November report in The Land quoted University of Canberra researcher, Dr Peter Unmack, who has two decades of experience working in the Murray-Darling basin. Unmack said disposal of carp carcasses would be a major concern, as decaying fish would pile up from the first week the virus was released. This would de-oxygenate water and harm native fish. “You would need a lot of people in boats with nets scooping up dead fish.”

In all that has been written and said about the release plan, there has been no detail provided about clean up, beyond vague talk about paying locals to remove and dispose of dead fish. The Lachlan is 1,440 kilometres long, the Murrumbidgee 1,600 and the Murray-Darling, 2,507km. Great stretches of these rivers are sparsely populated. No scenarios have been painted about how many people will be needed in the clean-up, covering how many kilometres, in how many boats, and across what length of time will be required to clean it all up. And in these small towns, how many people are sitting about ready to take to the boats?

A “thought bubble” solution”?

Matt Landos, a lecturer in aquatic animal health at the University of Sydney posted important comments on my last column on this issue.

Carp are vilified as a major cause of river turbidity or cloudiness. They suck up mud looking for food. Landos argued the evidence about carp being a major cause of river turbidity is conflicted in the research literature on the issue. In 1985 Fletcher and others said of a Goulburn valley study:

There was no association between high carp densities and high turbidity, and populations of carp did not appear to increase turbidity. Observed turbidity increases at each site appeared to be related to hydrological changes. Fluctuation of water levels was also an important factor determining the extent of aquatic vegetation communities.

Landos also noted King et al (1997) had stated:

factors other than carp usually contributed to most of the variation in measured water quality in Murrumbidgee billabong.

They also observed:

Cattle grazing and clearing has altered the vegetation communities of the floodplain in this region. The floodplain vegetation now consists of scattered mature river red gums. The understorey is dominated by introduced grass and weed species. Owing to the drought conditions and grazing by cattle, vegetation in the catchments surrounding the billabongs was sparse during most of the study period; this and heavy rain towards the end of the experiment combined to cause significant sediment loss from the adjacent hills.

Dr Landos also notes carp are highly unlikely to be the primary driver of native fish declines, though often blamed. To blame carp, is to ignore the swathes of literature on the reasons native fish reproduction has failed including: loss of passage/access due to dams, weirs and irrigation gates; cold water pollution obliterating the spawning signals; pesticides killing and deforming larvae; fertiliser promoting toxic algae; salinity impacting egg hydration; and loss of habitat.

Carp have few friends. Unlike in other parts of the world, few are eaten in Australia. They are an easily scapegoated target. The herpes release seems highly likely to cause massive problems that have to date only been sketched. And all agree that while the release will reduce carp numbers dramatically, it will not eradicate them. If Landos and the researchers he cites are correct, this exercise may do little to improve water quality in our rivers either and may have signiicant collateral impacts.

The Conversation

Simon Chapman, Emeritus Professor in Public Health, University of Sydney

This article was originally published on The Conversation. Read the original article.

Carpageddon: what you need to know about the release of carp herpes in Australia

Susan Lawler, La Trobe University

Yesterday’s announcement of funding for a National Carp Control Plan – including the release of the carp herpes virus – has generated a lot of interest in the media. I welcome plans to release the virus by the end of 2018. In January I wrote an article here explaining the concept and why I think it could work in Australia.

Since the announcement I’ve listened to discussions on radio and television highlighting the concerns of the public. I hope to address some of the confusion and set the record straight.

What will we do with piles of dead fish?

Among people who live near the Murray River or one of its tributaries, this is the main objection to the release of the virus. This in itself suggests that those close to the rivers understand the implications of carp being 80% of the biomass in the Murray Darling Basin. Many people have lived through black-water events (where oxygen levels drop resulting in large fish kills) and they know how unpleasant it is to have a lot of dead fish at one time.

Their concerns are justified. Fortunately, Science Minister Christopher Pyne is aware that hundreds of thousands, possibly millions of tonnes of dead carp will need to be cleaned up, and this will require community consultation and potential legislative changes. Pyne says we can use dead carp as fertiliser, as pet food or bury them in large graves. It is interesting to note that the fertiliser company Charlie Carp welcomes the move and may expand their business into South Australia so they can respond to large fish kills there.

The trick will be disposing of the fish quickly because after 48 hours they will begin to rot and will not be suitable for use. My reading of the announcement suggests that planning for this one time big carp kill will be a large part of the $15 million spent over the next two years.

How is the virus transmitted?

There were some giggles about how this virus is transmitted among fish, given that herpes is a sexually transmitted disease in humans. However, all the fish have to do is bump into one another to transmit the virus, and they can also be infected by the virus that lives in the water, although the virus will only survive for a few days outside of the body of a fish.

Once infected, any survivors will carry the carp-specific herpes virus for life. Stress can re-activate the virus, causing it to persist in the carp population and allowing it to spread rapidly under crowded conditions.

What a waste – we could have sold these fish overseas!

It is true that Australians resist eating carp due a perception that they are “junk” fish. Some say they have a muddy flavour, or that they are too bony. Neither of these issues stop people in Europe, the Middle East and Asia eating carp, where they are a common part of the diet.

There are two problems with the suggestion that we are missing a commercial opportunity here. The first is the economic viability of shipping fish to the other side of the world. We cannot get them there alive so we will need to freeze or can the carp, and once we’ve done that, consumers must pay enough to cover the processing and shipping.

I was on a committee with the NSW Department of Fisheries 15 years ago that was looking for markets for carp products. Enthusiastic investors with support from government could not find a way to make money with this export.

The second problem is that any industry relying on carp as a product will not remove carp from our rivers. Carp are causing enormous damage to the ecology of rivers and lakes across our continent and fishing alone will never remove enough of them to return those ecosystems to health.

But biological control never works, does it?

“Myxomatosis and cane toads – need I say more?” was a text to my local ABC radio station by someone concerned about the failure of biological control in the past. Yes, cane toads were a disastrous introduction to Australia and it is now clear that the problem was insufficient research prior to release. The carp herpes virus has been researched in Australian laboratories for 7 years so far. See my previous article for more on why this looks like a safe bio-control option.

Myxomatosis actually worked beautifully, killing 500 million rabbits in two years after the first release in 1950. Resistance did increase in the decades to follow and in 1996 another virus (calicivirus) was released to further reduce rabbit populations.

The rabbit plague of 1860 onward was the fastest spread of any mammal in the world. Rabbits had an enormous environmental and economic impact right across Australia, leading us to build the rabbit-proof fence. In 1887 the state of New South Wales was offering a reward of £25,000 for any successful method not previously known for exterminating rabbits. Although srabbits were useful for food in the depression and to make lots of hats, nobody wants to return to pre-myxomatosis times.

And no, we didn’t kill all the rabbits, just like we will not kill all the carp. However, a virus transmitted by water may be more effective as suggested by the government’s goal of a 95% carp reduction by 2045.

Carp are natural by now – our native fish rely on them for food

Australian native fish have been seriously impacted by carp. Many of them are visual predators, such as the magnificent Murray Cod. The turbidity created by carp reduces their ability to hunt and thrive, even though the high biomass of carp may give them plenty to eat.

The muddy river that runs through my home town is a hazard for swimmers and boaters because you can’t see the snags. This is due almost entirely to the presence of carp. None of us can remember when the Murray River ran clear and native fish were more common than introduced fish, but Senator Anne Ruston, Assistant Minister for Water Resources, recalls her mother and grandmother talking about being able to see the bottom of the river.

If you cannot imagine why anybody cares what type of fish are living in our rivers, remember that native Australian fish and plants are not adapted to the muddy rivers we have now. Let’s give them a chance to grow and thrive again in an environment more similar to the natural situation.

Sounds like a waste of money

Our Deputy Prime Minister Barnaby Joyce says that carp cost the economy up to $500 million per year. I don’t know how he got that figure but it may include the extra water treatment we need for river towns like mine and tourism losses due to reduced biodiversity and frequent algal blooms. Even if it is only half of that, spending $15 million to remove carp from the system seems like a sound investment.

The future of Australia’s waterways are at stake. Is there anything more precious than clean, fresh water?

The Conversation

Susan Lawler, Senior Lecturer, Department of Ecology, Environment and Evolution, La Trobe University

This article was originally published on The Conversation. Read the original article.

We could reduce pest carp in Australian rivers using a disease that came from Israel

Susan Lawler, La Trobe University

Everyone wants to give Australian carp the herpes virus. That’s right, introduced carp are a serious pest species and research suggests that a viral control agent may be the most effective solution.

I love stories like this one, where groups that would normally disagree come together in an “unlikely coalition”. That is to say, fishers, conservationists, irrigators, scientists and farmers agree on the desirability of an environmental release of the carp-specific virus.

After all, it worked for rabbits. The release of the myxomatosis virus in the 1950s and the more recent release of calicivirus have permanently decreased rabbit numbers on our continent. Using viral pathogens to control vertebrate pests can be extremely effective because it does not require ongoing human intervention.

Like rabbits, carp were introduced to Australia deliberately. The first introductions in the 1800s did not cause problems, but a strain bred for European aquaculture escaped from farm dams near Mildura in the 1960s and spread throughout the Murray Darling Basin. The impact of carp on our rivers has been well documented, including increasing turbidity (making the water muddy), destroying aquatic vegetation, and contributing to the decline of native fish.

In other parts of the world, carp are an important food species, often raised in fish farms. When I worked on a kibbutz in Israel in 1980 we caught and sorted carp from geothermal pools near the Sea of Galilee. The fish were a desirable food item and water from the fish ponds was used to fertilise banana crops via drip irrigation. I admired the sustainable farming practice that was then ahead of its time.

Twenty years later while participating in a fish survey at Horseshoe Lagoon near Albury, I remember pulling dozens of giant carp out of our nets, lamenting the lack of native fish. Because we were not allowed to return the carp to the water due to its pest status, we had to kill each one, resulting in a large pile of stinky dead fish that nobody wanted to eat.

The only similarity between these two memories was the method of death: although it looks brutal and cruel, hitting carp on the back of the head with a heavy wooden stick dispatches them instantly and humanely. On those two occasions this peaceful vegetarian turned into a lethal killing machine.

Ironically, at about the time I was whacking pest carp in Australia, the carp industry in Israel was affected by a new disease. The koi herpesvirus, or Cyprinid herpesvirus 3 (CyHV-3) appeared in Israel in 1998 and was so contagious that it soon spread throughout Europe and Asia. The carp industry was devastated.

While this virus is bad news for carp farming, it could be good news for managing feral carp in Australia. With an expected mortality rate of 70-80%, CyHV-3 may be just what we need to curb the plague of carp in our rivers.

Of course, given our sometimes disastrous experience with biological control species, caution is warranted. That’s why scientists have spent the last eight years doing research to ensure that the herpes will not affect other species. Ken McColl is a leader of the team that has examined the host specificity of the virus in an Australian context.

The good news is that CyHV-3 has no impact on other native fish, yabbies and trout. It cannot infect mammals, amphibians or reptiles. In other words, it looks safe.

The bad news is that it will affect ornamental carp (koi) which are highly valued, so people who keep koi will need to monitor their water and food sources. I see this as something like vaccinating your pet rabbits against calicivirus, an inconvenient but reasonable impost given the benefit for the nation and our environment.

What happens now? There are a number of government organisations that are responsible for biosecurity. Getting approval to introduce a virus into our waterways will probably take a few years, so the research will continue as the Invasive Animals Cooperative Research Centre goes through the application process.

There is also research underway to identify locations suitable for early releases, and this is where members of the public can get involved. Hotspots for invasive fish species will be identified by gathering data from concerned citizens at a new website called Feral Fish Scan. Anyone interested in learning how to identify invasive fish and record observations of their local waterways can do so at this link.

Other conventional approaches to reducing carp are still underway, from the development of traps that target carp to better ways for Charlie Carp to turn those feral fish into fertiliser. But harvesting tons of carp and turning them into pellets will never reduce the impact of this noxious pest as effectively as a carp-specific disease.

This is why virtually everyone is excited about the possibility of giving herpes to Australian carp. And even though I think it sounds like a good idea, I am also grateful that we have robust regulations about biocontrol, because there was a time when cane toads seemed like a good idea, too.

We can wait a couple of years to ensure that we do not regret our decision, but then we may enjoy a great irony: a disease that caused huge financial losses overseas could save freshwater environments in Australia.

The Conversation

Susan Lawler, Senior Lecturer, Department of Ecology, Environment and Evolution, La Trobe University

This article was originally published on The Conversation. Read the original article.