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In muddy waters: the plight of Australia’s threatened freshwater mussels

Freshwater mussels, like other freshwater animals, are disappearing at an alarming rate. They are invertebrates, and while invertebrates may account for 95-99% of animal biodiversity, they are scarcely…

Australian freshwater mussels are under threat from habitat erosion. Crawford River/Photo by MW Klunzinger

Freshwater mussels, like other freshwater animals, are disappearing at an alarming rate. They are invertebrates, and while invertebrates may account for 95-99% of animal biodiversity, they are scarcely on our radar in matters of conservation. Worldwide, they are one of the most imperilled groups of fauna, particularly due to the scarce and often abused resource which they inhabit: precious fresh water.

Freshwater mussels are natural water filters, cleaning the water by removing particulates, algae and zoo-plankton. They also promote nutrient cycling and remove heavy metals, pesticides and a variety of other pollutants from water, making them useful as biological monitors but much less attractive as something for us to eat.

I never thought I would be an advocate for a creature so inconspicuous it is hardly more appealing than the alga-covered stones that lie next to it in the stream bed. That was until I found out about the intriguing, fascinating life cycle of a freshwater mussel.

Their larvae, known as “glochidia”, attach to certain species of freshwater fishes and undergo metamorphosis to emerge as juvenile mussels. This distributes new recruits over much greater distances than an adult mussel could ever hope to move.

Australia is one of the driest and most isolated places on the planet. It comes as no surprise then that, what the country lacks in richness of freshwater mussel species, it makes up for in uniqueness.

Australia has at least 18 species in a single family, found only in Australasia and South America. Several species are at risk and two qualify for conservation listing.

Freshwater mussels are disappearing at an alarming rate. Photo by DL Morgan

Already, mussels have disappeared from many streams in eastern Australia from loss of catchment vegetation in association with agricultural development. The habitats in many streams have become degraded from channel erosion and sedimentation. Increased nutrient loads in runoff, loss of shading vegetation and invasive water plants like Salvinia molesta and water hyacinth (Eichhornia spp.) have badly affected mussels in some parts of Australia.

Efforts have been made to bring the plight of the freshwater mussel to the attention of conservation bodies. Species such as the Glenelg River Mussel (Hyridella glenelgensis) have been recently listed as “Critically Endangered” under the Victorian Flora and Fauna Guarantee Act 1988 and the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act).

In the mid-1990s, Carter’s Freshwater Mussel (Westralunio carteri) in south-western Western Australia was listed as “Vulnerable” on the IUCN Red List and recognised as a “Priority 4” species (a species in need of monitoring) by the WA Department of Environment and Conservation and, more recently, nominated for listing under EPBC criteria following a four-year study at Murdoch University.

Mussels are natural water filters but poor water quality and salinity are reducing their numbers. Photo by MW Klunzinger

Inaction on our part is one of the main dangers for the species. Often a species fails to qualify for listing because we don’t have the necessary data to assess it against conservation criteria. Where published data is lacking, we often need to scrutinise museum collections for historic records of species and re-visit those sites to detect declines.

But in some cases inaccurate or vague records make pinpointing species distributions difficult. Defining species distributional boundaries and the declines in the extent of occurrence is also difficult where data is lacking. Without accurate age data, we can’t determine “generation length”, and this also hinders conservation assessment. Generation length is the average age of the parents of newborn individuals in a population.

This is an important criterion used to determine conservation of a species in the IUCN Red List Guidelines. Furthermore, mussels’ patchy distribution combined with difficult-to-access localities, and the labour-intensive survey methods required, make population estimates difficult to obtain.

In Victoria, H. glenelgensis appears in a very short section of stream. It is threatened by siltation and loss of riparian vegetation from cattle trampling and overgrazing, as well as poor water quality including salinity and possibly pesticides and flow reductions. The invasive Carp (Cyprinus carpio) is another reason for major concern.

In south-western Australia, W. carteri has disappeared from more than half of its former range due to salinity from land clearance and the drying of habitats resulting from climate change and increased demand for dwindling water supplies in a rapidly expanding urban population. Cattle trampling, siltation and loss of riparian vegetation are also causing declines in rural areas.

Habitat rehabilitation, species recovery plans and follow-up monitoring are critical to allow sensitive species such as freshwater mussels to flourish. Community-based conservation science programs and cost-shared, not-for-profit conservation initiatives appear to be the way forward.

That is because most threatened species exist on private land. In some districts, landowners have banded together to protect long sections of stream.

This strategy has worked well in some areas, but needs to be led by expert scientists, governments, industry and a community working together.

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13 Comments sorted by

  1. Mike Jubow

    forestry nurseryman

    Very Interesting. Would I be correct in presuming that a large population of mussels is an indicator of a healthy waterway? There are plenty of mussels to be found in the creek at almost any time when the creek isn't running a banker. Our creek which runs for at least 9 months of the year has a good population of tortoises, sleepy cod, fork tail catfish, spangled perch barramundi, water dragons and the occasional croc or three.

    There are cane farms on both sides of the creek for most of its length right up to its headwaters some 10 km above us. One would hope that the influence of farming is having minimal impact on our creek.

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    1. Dianna Arthur
      Dianna Arthur is a Friend of The Conversation.

      Environmentalist

      In reply to Mike Jubow

      Mike, thanks for your work in observing the fauna of your local waterways. Frogs are not the only indicator of the health of ecosystems.

      And many thanks to author, Michael Klunzinger for a highly readable and informative article, more please.

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    2. Michael Klunzinger

      Dr - Honorary Research Associate - School of Veterinary and Life Sciences at Murdoch University

      In reply to Mike Jubow

      Dear Mike Jubow,

      Thank you for reading the article. Your question about a large population of mussels as an indicator of a "healthy" waterway is dependent on how we define river "health". Strictly speaking, a waterway which is entirely unhealthy would not support any life whatsoever, which is extremely rare even in the most polluted rivers.

      However, I think the general consensus amongst conservationists is that a greater concentration of native, and especially endemic flora and fauna may…

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    3. Michael Klunzinger

      Dr - Honorary Research Associate - School of Veterinary and Life Sciences at Murdoch University

      In reply to Dianna Arthur

      To Dianna Art,

      Thank you for your comment. I agree that frogs are really good indicators too, given their sensitivities.

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    4. Dianna Arthur
      Dianna Arthur is a Friend of The Conversation.

      Environmentalist

      In reply to Michael Klunzinger

      Thank you for your replies to readers and the most excellent work - we need more people understanding the balance of the environment in which we live.

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    5. Mike Jubow

      forestry nurseryman

      In reply to Michael Klunzinger

      G'day Michael, thanks for the feedback. I was motivated enough to go down to the creek today to see if there were any junior versions of the mussels and within minutes I found plenty. Had only observed the obvious ones before because they were the largest.

      I do take you to task about the creekside vegetation having to be native. I am a passionate tree grower that wants to do the best for the land and still make a quid from the timber. I grow mostly exotic rainforest timber trees right down to…

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    6. Michael Klunzinger

      Dr - Honorary Research Associate - School of Veterinary and Life Sciences at Murdoch University

      In reply to Mike Jubow

      Hi Mike,

      Thanks for your response. You have some good points, but I think we might be straying away from the topic of freswhwater mussel conservation and the conservation of Australia's native species, which was the topic I was invited to cover for this article. All the best.

      Michael.

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  2. Lee Emmett

    Guest House Manager

    Buddhist teaching emphasises interdependency: every-thing and every-one is related. This concept, translated into action, means that every act needs to be considered for its impact on others and the environment. Several years ago I contributed to a strategic plan for integrated catchment management, where every part of the water flow, from mountain to the sea, was considered vital to the health of the total living system. The strategy proposed that volunteers ('Friends' groups), schools, industries…

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    1. Rotha Jago

      concerned citizen

      In reply to Lee Emmett

      Maybe "Eliminating pest weeds" might be one cause of the decline of the mussels. Glyphosate is now used extensively by Councils and landscapers as a way of 'tidying' landscapes. Weedy or ragged edges are no longer acceptable it seems. In Queensland our previous government insisted that Councils use Glyphosate on creek banks, in parks on roadsides and rail corridors in the belief that it was benign.
      The environmental change locally is distressing, but Council contractors go on spraying in wet weather…

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    2. Michael Klunzinger

      Dr - Honorary Research Associate - School of Veterinary and Life Sciences at Murdoch University

      In reply to Lee Emmett

      Hello Lee,

      Thanks for your comment. While I have not studied Buddhism in depth, from what I do know of it, the web of life and perhaps the analogy that every action has an equal and opposite reaction (Sir Isaac Newton's 3rd Law in Physics). I am an advocate for community action and education and I wish that more institutions recognised its importance. That is where the change comes from and ICMP is a shining example of positive steps forward. I am currently working on such a documentation and would love to speak with you more and connect you with the community organisation I work with to build more positive bridges. Good onya :)

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    3. Michael Klunzinger

      Dr - Honorary Research Associate - School of Veterinary and Life Sciences at Murdoch University

      In reply to Rotha Jago

      Dear Rotha Jago,

      Thanks for your comments,

      I'm not sure I could answer your concerns, but do agree this issue needs to be looked at more carefully. I was shocked to find out that toxicology information for these chemicals on aquatic fauna, LD50, LD95 and safe operating limits are not well known for Australian flora and fauna. Compliance and enforcement also, in my experience, have been lacking. I am not an expert on die back, but from what I understand, die-back in trees can have a number…

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  3. Tamara Kelly

    teacher

    Thanks for writing this article because I have been wondering how I can increase the mussel numbers in my dam and creek. I am guessing the way to grow their numbers is to ensure a healthy riparian zone. Is there anything else I can be doing to encourage their numbers?

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    1. Michael Klunzinger

      Dr - Honorary Research Associate - School of Veterinary and Life Sciences at Murdoch University

      In reply to Tamara Kelly

      Hello Tamara,

      Thanks for your interest,

      A healthy riparian zone certainly can't hurt. Maintaining connectivity between dams and creeks or rivers to allow fish movement is a hot topic as well. Freshwater mussels require that native freshwater fishes are available for the larvae to attach to fishes to complete the life cycle to the juvenile mussel stage. Very little is known about the juvenile freshwater mussel stage. I hope to network with enough of the right people to convince decision makers to invest in such research.

      Regards,

      Michael

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