* The Darling River has seen many fish deaths over the past month

* Many of the fish were nationally endangered species such as Murray cod

* CSU experts share their views on the continuing crisis

The fish deaths in the Darling River at Menindee have resulted in devastating impacts on endangered fish populations and water quality.

With expertise in the ecological, social and economic impact of the crisis, researchers from Charles Sturt University’s Institute for Land Water and Society (CSU-ILWS) share their thoughts.

Associate Professor Andrew Hall, Climate and Spatial Scientist, Associate Director ILWS

“Reduced flow through water extraction compounded with increasing temperatures and rainfall variability through climate change leads to higher probabilities of extreme low flow conditions in downstream areas of large water catchments. Extreme events such as that currently occurring in the Darling River need to be considered as likely scenarios requiring contingency management plans.

Actively planning water use to mitigate future potential low flow events is clearly essential to sustain the globally significant freshwater ecosystems of the Murray-Darling Basin. Adequate water volumes must be maintained for environmental use to ensure connectivity and flow for an increasingly drought and heatwave prone climate.”

Dr Paul Humphries, River ecologist

“Murray-Darling Basin rivers have been subject to a range of stressors for more than a hundred years, and declines in diversity, numbers and ranges of fish species over that time, are a direct result of those stressors.

It is not a surprise that when a dry period combines with extreme temperatures and is added to an already-stressed system, it will reach a tipping-point.

Although the fish kills are shocking, we should see the situation as a wake-up call: not only for on-going water reform and a more realistic and appropriate allocations of water for the environment, but also for understanding about how the system has reached the state it did and how it recovers.

We desperately need to understand the sequence of events that led to the conditions that caused the kill, how extensive the poor water quality is (why do some areas have fish kills and others do not?) and the nature of the process of recovery. Without ongoing commitment at the highest government level to understanding such processes, such events are going to increase in frequency, extent and severity.”

Associate Professor Skye Wassens, Ecologist

“Fixing rivers is simple - it’s just not easy.

The solutions to the continued degradation of aquatic ecosystems are simple: provide more water for the environment, restore and prioritise water for the environment at critical times (for example during periods of water scarcity), remove barriers to fish movement and promote river flows that restore natural river and floodplain reconnections.

But of course it’s not that easy - irrigation industries underpin many rural economies, droughts and low allocations also mean job cuts and significant economic hardships for communities.

In the Murrumbidgee River system, we were fortunate to have just enough water in the environmental water holding to be able to deliver refuge flows to key fish habitats, small flushes are still being delivered through the river to help reduce risks of algal blooms. These actions involve considerable planning, they are robustly monitored so that we can learn, adapt and improve our approach in future years. Most importantly these environmental actions are supported by communities and the large irrigation areas that share the river.”

Dr Lee Baumgartner, Ecologist - Fisheries and River Management

“We have scientific evidence that the Lower Darling (downstream of Menindee) is an important source of fish recruitment in SOME years. In 2009 a lot of fish from the mid-Murray region (and the lower Murray in SA) had chemical signatures suggesting they were spawned in the Lower Darling. So, there is some connectivity between the Darling and other sections of the “Lower Connected Basin. Golden perch and Murray cod live a long time (GP up to 30 years; MC up to 60 years). Replacing old fish takes that long if the fish need to grow from larvae. However, large-old fish may migrate into this reach, from other reaches, once flows return. So there are two mechanisms for recovery. Larvae may drift from upstream into the reach, and big fish may migrate downstream.

A 2012 fish kill in the Edward-Wakool system was similarly devastating. Fish deaths occurred from Barmah forests, through the Edward system all the way to South Australia. The causes were, however, different and during the event, refuges were created to protect “pockets” of fish. Fish that survived recolonised the system within five years. Murray cod and golden perch migrated into the affected regions quickly and larvae drifted downstream. Fish were re-stocked but the majority of fish were naturally spawned. These systems are resilient and can bounce back quickly when the conditions are right.”

Dr Jonathon Howard, Environmental Sociologist

“There is no reason for us to accept algal blooms as a ‘recurrent norm’. I appreciate reconciling the demands for freshwater by agriculture with finite freshwater resources remains one of the great policy dilemmas on our planet. However if communities in the Basin are going to survive into the future we have to learn to live together.

Now turning to the question about water management. We need to change. The current approach encourages mismanagement and ‘gaslighting’ by lobby groups, industry, and government.  To be clear, I am not blaming government - but more specifically ‘governance’. My opinion is based largely on how the: i) politics of climate change has affected planning in the Basin; ii) how de-democratisation has limited wider public participation, and iii) how the idealism associated with economic rationalism has dominated operations. All these pressures have cruelled our ability to manage one of our greatest natural resource assets.

In sum, the recent fish kill is a bloody mess at a scale. And not just for wildlife, but also the local community, indigenous custodians, and a range of stakeholder groups.

The question is can we change in time? Simply suggesting we put fish back into a river when it has no water is no answer.”

Dr Julia Howitt, Environmental Chemist

“What we have done in the past is work with water managers during water quality crises to understand what options they have available to them and in an individual crisis to try and minimise the impact on the fish.  We know that being able to do that requires understanding what is happening to the water quality in that place at that time.

We have the capacity to work with people to help them respond to a water quality crisis.

A big algal bloom won’t always result in the water quality conditions that will cause a fish kill event. Conditions of the algal bloom can change over time due to daytime and overnight temperatures, wind and introduction of new water sources.

To be able to manage an event like the one in the Darling River requires on-going monitoring and understanding of the water quality.

There is no one size fits all approach to manage these things, you have to look at each specific event.”

Dr Keller Kopf, Fish Ecologist

“Heat waves, hypoxia and dead fish: it's time to change Australia's water, land-use and climate policies.

Extreme climate events, blue-green algae, hypoxia, deaths of native fish and other species now occur regularly in the waterways of Australia. Even in the world's driest inhabited continent, the frequency, severity and extent of these events is higher than many native species and ecosystems can withstand.

The ultimate cause of these fish-kills is poor water quality due to the over-allocation of water and flow alteration. The increasing severity is exacerbated by unsustainable land-use practices and climate change. With soaring temperatures and hypoxic rivers this week, we are at the coalface of unsustainable water, land and climate change policies.

Australia's water, land-use and climate policies are unsustainable and must change now if society wants to avoid worse fish-kills, hotter temperatures and uninhabitable waterways. “

Adjunct Professor Peter Waterman RFD, Geographer

Area of expertise:  Integrated catchment and coastal zone management, climate change adaptation, environmental assessment, sustainable regional development

“Assured supplies and reduction of health risks from unsafe water must be a priority for towns and communities across the Murry Darling Basin (MDB). Currently, the cumulative effects of drought, no-flow and microbiological conditions have adversely impacted on the adequacy and quality of domestic supplies in the Central and Lower Darling. Consequently, the statutorily based objectives of ‘critical human water needs’ for the MBD are not being met.And these are defined in subsection 86A of the Water Act 2007 and Chapter 11 of the Basin Plan and cover all uses of surface and ground water for domestic purposes.

Currently, the sufficiency and quality of these resources is largely unknown and the potential health risks arising from this situation are not being addressed.

And this deficiency has implications for economic productivity and the quality of life for people in the Basin, and it should be addressed as matter of urgency.”