River Murray | ConservationBytes.com

Interrupted flows in the Murray River endanger frogs

17 01 2023

Flooding in the Murray-Darling Basin is creating ideal breeding conditions for many native species that have evolved to take advantage of temporary flood conditions. Led by PhD candidate Rupert Mathwin, our team developed virtual models of the Murray River to reveal a crucial link between natural flooding and the extinction risk of endangered southern bell frogs (Litoria raniformis; also known as growling grass frogs).

Southern bell frogs are one of Australia’s 100 Priority Threatened Species. This endangered frog breeds during spring and summer when water levels increase in their wetlands. However, the natural flooding patterns in Australia’s largest river system have been negatively impacted by expansive river regulation that some years, sees up to 60% of river water extracted for human use.

Our latest paper describes how we built computer simulations of Murray-Darling Basin wetlands filled with simulated southern bell frogs. By changing the simulation from natural to regulated conditions, we showed that modern conditions dramatically increase the extinction risk of these beloved frogs.

The data clearly indicate that successive dry years raise the probability of local extinction, and these effects are strongest in smaller wetlands. Larger wetlands and those with more frequent inundation are less prone to these effects, although they are not immune to them entirely. The models present a warning — we have greatly modified the way the river behaves, and the modern river cannot support the long-term survival of southern bell frogs.’

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Tags: amphibian, Australia, biodiversity, climate change, conservation, ecology, environment, Litoria raniformis, southern bell frog
Categories : Australia, biodiversity, climate change, connectivity, conservation, demography, drought, ecology, environmental policy, extinction, flood, frog, management, metapopulation, minimum viable population, modelling, Murray River, Murray-Darling, population dynamics, population viability analysis, PVA, River Murray, South Australia, southern Australia, stochasticity, threatened species, water, weir gates

The integrity battlefield: where science meets policy

4 03 2022

Professor Ross Thompson, University of Canberra

On the whole, I am inclined to conclude that my experience of academia and publishing my work has been largely benign. Despite having published 120-odd peer-reviewed papers, I can count the number of major disputes on one hand. Where there have been disagreements, they have centred on issues of content, and despite the odd grumble, things have rarely escalated to the ad hominem. I have certainly never experienced concerted attacks on my work.

But that changed recently. I work in water science, participating in and leading multi-disciplinary teams that do research directly relevant to water policy and management. My colleagues and I work closely with state and federal governments and are often funded by them through a variety of mechanisms. Our teams are a complex blend of scientists from universities, state and federal research agencies, and private-sector consultancies. Water is big business in Australia, and its management is particularly pertinent as the world’s driest inhabited continent struggles to come to terms with the impacts of climate change.

In the last 10 years, Australia has undergone a AU$16 billion program of water reform that has highlighted the extreme pressure on ecosystems, rural communities, and water-dependent industries. In 2019, two documentaries (Cash Splash and Pumped) broadcast by the Australian Broadcasting Corporation were highly critical of the outcomes of water reform. A group of scientists involved in working on the Murray-Darling Basin were concerned enough about the accuracy of aspects of those stories to support Professor Rob Vertessy from the University of Melbourne in drafting an Open Letter in response. I was a co-author on that letter, and something into which I did not enter lightly. We were very concerned about being seen to advocate for any particular policy position, but were simultaneously committed to contributing to an informed public debate. A later investigation by the Australian Communications and Media Authority also highlighted concerns with the Cash Splash documentary.

Fast forward to 2021 and the publication of a paper by Colloff et al. (2021) in the Australasian Journal of Water Resources. In that paper, the authors were critical of the scientists that had contributed to the Open Letter and claimed they had been subject to “administrative capture” and “issue advocacy”. Administrative capture is defined here as:

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Tags: Australia, climate change, co-authorship, ecology, environment, environmental policy, ethics, Global warming, integrity, MDB, Murray-Darling Basin, policy, publishing, river, science, science-policy interface, scientific principles, scientific rigour, water
Categories : Australia, climate change, drought, ecology, environmental economics, environmental policy, environmental science, ethics, governance, management, modelling, monitoring, Murray River, Murray-Darling, planning, research, River Murray, science, science writing, scientific writing, southern Australia, water

How to fix a broken river

5 04 2019

murraycod

It seems that most of what I do these days is measure, model, or otherwise quantify environmental damage. While I dabble in restoration, occasionally I’m involved in a project that really can make a positive difference.

If you’re an Australian, you’ll know a thing or two about just how much of a clusterfuck our biggest river system has turned into. From mismanagement, to outright theft, to lobbyist-driven over-exploitation, to climate change itself, the Murray-Darling system is now in a right mess.

So, I’ll pretext this post with a caveat — no amount of ecological restoration can ‘fix’ a compromised river if there’s no water in it. Goes without saying, really.

But, if you do have water, then there are things one can do to promote populations of various creatures living in it, like fish.

Dubbed the ‘honeypot effect’ — we have just shown that providing woody habitat, or ‘snags’, for native fish in the Murray River increases population size. Read the rest of this entry »

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Tags: aquatic, ecological restoration, ecology, golden perch, Murray cod, Murray-Darling, rehabilitation, restoration, snags
Categories : Australia, conservation, conservation ecology, fish, fisheries, Murray cod, Murray River, Murray-Darling, restoration, River Murray, South Australia, southern Australia, water

Restoring doomed fish

24 08 2012

I get called a doomsday merchant a lot, mainly because there’s not a lot of good news out there when it comes to biodiversity these days. However, now and again there is a success story worth shouting from the rooftops. This latest post comes from my PhD student, Jarod Lyon (also of the Arthur Rylah Institute in Victoria), who is working on restoring native freshwater fish in Australia’s largest river system – the Murray-Darling. The M-D also happens to be in a lot of trouble because of poor water management and years of neglect. However, some clever research and restoration proves that we can bring biodiversity back from the brink if done right. Jarod has posted here on Conservation Bytes before describing his work, and this latest post provides some detail on one species in particular.

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Trout cod Maccullochella macquariensis were once considered to be widespread in the southern tributaries of the Murray-Darling Basin. However over the past fifty years, their distribution and abundance have declined dramatically, due to a number of disturbances including habitat loss, altered flow and temperature patterns, in-stream sedimentation, population fragmentation due to in-stream barriers and over fishing. Trout cod are listed nationally as endangered under the Environment Protection and Biodiversity Conservation Act (EPBC Act 1999) and listed under the Victorian Flora and Fauna Guarantee Act (FFG Act 1988). Trout cod are often accidentally caught when fishing for Murray cod. However, it is illegal to take a trout cod while angling.

Trout cod were historically abundant in the lower Ovens River system in South-Eastern Australia, however were locally extinct by the 1980s. In an attempt to re-introduce a viable population in the Ovens River, hatchery-reared juvenile trout cod were stocked in the Ovens River system for ten years starting in 1997. Our recent manuscript published in Marine and Freshwater Research assesses the success of this stocking regime (particularly in relation to recovery plan objectives) through a variety of techniques, including fish surveys and analysis of gonads, otoliths and genetic structure of the population.

We found that the Ovens River now holds a naturally self-sustaining population of trout cod – that is, the progeny of stocked fishes are now breeding. Given that most threatened species re-introduction programs worldwide fail, this is somewhat of a good-news story for management of rare animals. In particular, we found that the length of the stocking program was a major factor in its success, as the long time period overcame the years where the survival of the stocked fingerlings was low. Interestingly, most fish to recruit to an adult size were stocked in 2003 or 2004 – meaning if this had been a five-year program, it would most likely have failed. Read the rest of this entry »

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Tags: Endangered species, Environment Protection and Biodiversity Conservation Act 1999, Murray Darling Basin, Ovens River, recovery, restoration
Categories : Australia, conservation, decline, fish, fisheries, genetics, habitat loss, management, Murray cod, research, resnagging, restoration, River Murray, southern Australia, trout cod

Fishing for conservation

3 04 2009

Here’s a guest post from one of my newest PhD students, Jarod Lyon of the Arthur Rylah Institute in Victoria. He’s introducing some of his ongoing work and how he incorporates anglers into conservation research.

As most conservationists know, snags (fallen trees and branches in rivers) are the riverine equivalent of marine reefs, providing critical habitat for many plants and animals, from microscopic bacteria, fungi and algae through to large native fish. They are the places where the greatest numbers and diversity of organisms occur in lowland sections of rivers. Their presence has an important influence on the overall health of these rivers.

: Figure 1

Ins southern Australia, Murray cod, trout cod and golden perch are three iconic fish species that occur in the Murray River (Figure 1). Recent investigations into the ecology of these species have demonstrated a strong dependence on the presence of snags – a relationship well-known to recreational anglers who target both Murray cod and golden perch. Unfortunately, the abundance of these species has declined over the past 100 years and they are now considered threatened. Excessive removal of snags has been identified as a primary cause for this decline. For example, in the Lake Hume to Lake Mulwala reach of the Murray River, over 25000 snags were removed in the 1970s and 1980s to improve the passage of water between Lake Hume and the large irrigation channels at Yarrawonga.

: Figure 2

The largest resnagging project ever undertaken in Australia is now in full swing. It aims to reverse the legacy of clearing snags that has occurred along the Murray reaches since European settlement. The resnagging is occurring in the Hume-Mulwala reach of the Murray using trees that were cleared for the Hume Highway extension between Albury and Tarcutta, and will create substantially more physical habitat for native fish in this reach of the river. By creating this habitat, the size of the native fish population in this reach is expected to increase thereby improving the conservation status of the native species present, and improving the quality of the recreational fishery for native species (particularly Murray cod and golden perch). It is the largest project of its kind ever undertaken in Australia, and is a great step towards recovering fish populations. The project is funded under the Murray Darling Basin Commission‘s Living Murray Program, and is being undertaken by a variety of state and national organisations, in particular NSW Department of Primary Industries and Victorian Department of Sustainability and Environment (DSE).

To ensure that the resnagging is having a beneficial effect on the numbers of native fish in the reach, a comprehensive monitoring and evaluation program is being implemented by scientists from the DSE’s Arthur Rylah Institute. This program is determining whether an increase in the size of the native fish populations is the result of:

Increased recruitment in the reach
Increased survival of adults in the reach
Increased immigration of adults and juveniles form Lake Mulwala and the Ovens River
Decreased emigration form the reach

To measure these changes, the fish populations between Hume Dam and Lake Mulwala are being surveyed once a year to determine the population size and level of recruitment. For the purpose of comparison, surveying between Yarrawonga and Tocumwal, in the lower Ovens River, and in Lake Mulwala, is also being undertaken.

: Figure 3

Some of the fish caught (Figure 2) will be tagged with an external tag, internal tag or radio transmitter (Figures 3 & 4). All tags have a unique number that identifies the individual. The recapture of these individuals, both by researchers and by anglers, allows survival and movement patterns to be measured.

The external tags are plastic polymer tags and are easily visible, protruding from the dorsal fin area. These tags are used to allow information from anglers to be directly used in the monitoring. A phone number is printed on each tag and when anglers call this number to report that they have caught a tagged fish, this provides valuable information on the not only fish survival and growth, but also the performance of the recreational fishery. These tags have a lifespan of 2-5 years. Anglers who call in tag information are also eligible for a reward (usually a stubby holder or lure) and get sent a certificate which gives details of the history of the fish which they have captured and reported.

The internal tags are implanted into the area to the front of the pectoral fin, are not visible, and unlike the external tags, are permanent. The tags are passive integrated transponder (PIT) tags (Figure 4), similar to those used in the pet and livestock industry. The tags are important as they allow a long-term record of fish survival, growth and movement to be measured. Fishways across the Murray Darling Basin are increasingly being installed with readers that can detect these tags. This can give researchers valuable information on long-range movements. For example, one fish (a 20-kg Murray cod) that was tagged in the Murray river near Corowa, was picked up on a PIT tag reader at the bottom of the Torrumbarry Weir fishway – a fair feat when you consider that this fish has had to get through both Mulwala and Torrumbarry Weirs, as well as travel a distance of over 200 river km downstream!

: Figure 4

Radio transmitters are surgically inserted into the body cavity of the fish (Figure 3). These tags emit a radio signal that can be tracked continuously (Figure 5), and allow a rapid assessment of the movements (i.e., emigration and immigration rates) of a population to be determined. The tags are also detected by an array of 18 logging stations located along the river between Lake Hume and Barmah (Figure 1). Approximately 1000 radio tags will be implanted over the life of the project – making it possibly the largest radio-tagging program in the country.

If you catch a tagged fish, please record the type of fish, its number, its length (and its weight if possible) and the location of its capture and report this information on the phone number printed on the tag. These angler records improve the quality of the data collected and reporting of angler captures is encouraged through the rewards program.

As well as the general tag return program, a more targeted “Research Angler Program” is being undertaken. The angler program commenced operations in July 2007. The project was developed to assist with the scientific monitoring and communication requirements of the native fish habitat restoration project.

This section of the monitoring recognises that local anglers can contribute information about the state of native fish in the River Murray by recording their fishing effort and the amount of fish captured. Such information, in addition to greatly increasing the community awareness of the monitoring program, also adds another ‘string to the monitoring bow’ in that it will form a long-term dataset of fish captures, which can eventually be linked to the resnagging effort. The information gathered will be entered into a database and analysed to help assess changes in fish population size in relation to the habitat rehabilitation project.

Figure 5

Instream woody habitat is a vital component to the lifecycle of Murray Cod and the endangered trout cod. The resnagging of the River Murray – Hume Dam to Yarrawonga, will conserve and enhance native fish communities. Continual monitoring and interactions with the local angling fraternity is a crucial part of the success of this project.

The anglers have logbooks and have been trained in removing the otoliths, which are the earbones, from fish that they are taking for the table. We can then use the otoliths to determine the age and growth of the fish in response to the resnagging work.

Since December 2007 the fishers with the resnagging Angler Monitoring Program have captured over 65 Murray Cod, with over 95% of these fish released. Anglers have caught and released other native species such as golden perch and the endangered trout cod.