Black Water Kills Tens of Thousands of Murray Cod

Yesterday, Wakool farmer John Lolicato told me about recent fish kills in the southern Riverina.   Click here to listen to our conversation: WS450079   

The fish kills were caused by black water with tens of thousands of Murray Cod dying over the last four years.  

The enormous (1.4 metre long) Murray Cod being held up by two farmers is just one of many large fish found floating in the Lower Wakool River following a black water event last year.

The Wakool is an anabranch of the Murray, click on the map for a better and larger view.

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6 Responses to Black Water Kills Tens of Thousands of Murray Cod

  1. spangled drongo March 11, 2011 at 9:16 am #

    Jen,

    What a sad event. I have seen similar happenings with Yellow Belly in the deep, old water holes of the Channel Country. It is a natural occurrence but made a lot worse by bad management and poor understanding by those in authority.

    Another reason for MDB strategy to be revised.

  2. Binny March 11, 2011 at 9:30 am #

    A natural event that occurs in all of Australia’s inland river systems.

    Far from being a disaster the size of the fish involved indicates a healthy population in spite of years of drought.

    It’s interesting that smaller fish seem to be able to survive these events better than the larger ones. With no natural predators for those large cod, perhaps this is nature’s way of cleaning shop and allowing for a new generation.

  3. val majkus March 11, 2011 at 10:16 am #

    If I understood the tape correctly John Lolicato was saying that it was when the environmental flows occurred the fish died
    so I’m assuming that the black (or what we used to call ‘gummy’) water arrived with the environmental flows
    from my experience with black water shallow beds do become ‘black’ or ‘gummy’ as they dry up and become affected by dead leaves – the water turns black and fish die in that water and that water will not be drunk by stock
    all rivers have deep and shallow beds
    Where beds are deep in my experience only the perimiter water is affected and becomes black but this does not interfere with fish in the water further from the bank and fish can live quite happily in those conditions
    I think John Lolicato is saying that the environmental flows changed the usual course and allowed black water to flow into those deep beds which usually would not be affected
    If that’s the case it’s a shame the farmers are not listened to more

  4. susan March 11, 2011 at 11:21 am #

    Very sad to see these iconic fish end up this way especially after they’ve been tough enough to have survived the drought. Is anyone (EPA for example) monitoring the pH of the water in that area? Upon re-wetting of dried up wetlands that contain acid sulphate soils there can be a release of highly acidic water.

  5. Ian Thomson March 11, 2011 at 4:04 pm #

    Glad you two got together on this

  6. Geoff Sherrington March 11, 2011 at 7:06 pm #

    The last I studied inland water mass fish kills was from the Alligator Rivers Study team in the uranium province of the Top End, late 1970s I guess.

    IIRC, the first rains of the season are typically rather acidic, maybe from bushfire residues in the air. This early rainwater mobilises aluminium in particular and leads to toxicity in enclosed inland waters.

    Abstract from a mnore recent publication, http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8649.1983.tb04756.x/abstract

    A large natural fish kill which resulted in the deaths of a total of more than 3400 fish comprising eight different species occurred in a freshwater billabong (lagoon or small permanent waterbody) on the Magela Creek in the subtropical Northern Territory of Australia in January, 1980. The fish deaths were assessed to be the result of a combination of natural acid water runoff into the billabong and resultant elevated aquatic biotoxic aluminium levels. Details of water quality changes which occurred during the event and analytical data for the fish killed are provided, together with some explanation of the sequences of occurrence of the fish kill.

    I stress that this type of natural fish kill was common before mining started in the region – I have seen it personally, including upstream from mining – and that there is evidence from many places in Australia that it is part of the cycle of Nature.

    Unfortunately it seems to kill the bigger barramundi, but they are not of edible quality even if easily caught while still alive. I’ve seen several dozens over 5 kg each, clustered at the downstream ends of billabongs, hardly moving, dying before the proper rainy season.

    At such times the inland waters there do not appear particularly black. At a guess, I would say this was because of the different chemicals like tannins in the natural vegetation. Little colour in the Top End, lots in the Murray vegetation. Very few big trees like Red River Gums in the Top End, termites get them young.

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