The only freshwater mussel species in South-West Western Australia is in danger of extinction, Murdoch University researchers have warned.

Recent investigations into Carter’s freshwater mussel (Westralunio carteri) have revealed a dramatic decline in their range.

In a study published in 2015 in the Australian Journal of Zoology, Murdoch researchers led by Dr Michael Klunzinger found the range of Carter’s freshwater mussel had declined by almost 50 per cent in the previous 50 years, principally due to increasing salinity and a drying climate.

Over the last two years, Le Ma, a PhD student from Murdoch’s Centre for Sustainable Aquatic Ecosystems, revisited 47 areas where the mussel was thought to be present, and found it had disappeared completely from 13 (28 per cent) of these sites.

Associate Professor Alan Lymbery, who supervised the two studies, said the findings were concerning.

“Freshwater mussels are known as a keystone species – they filter an enormous amount of water as they feed, removing tiny particles like plankton, algae and microorganisms. This improves water quality and increases the productivity of aquatic ecosystems,” Professor Lymbery said.

“If this species is lost from our rivers and streams, there is nothing else that will carry out the same functions and that may have dramatic consequences for all freshwater life.

“During the summer and autumn months, when many rivers stop flowing, freshwater organisms such as our unique South-West fishes rely on refuge pools to survive. Mussels play an important role in maintaining water quality in these pools.”

Other impacts on the mussels include pollution, drought, temperature change and the loss of native fish that are necessary to their life cycle.

Larval mussels attach themselves to native fish to distribute their population.

Carter’s freshwater mussels are currently listed as vulnerable by international, national and state agencies, but there are no conservation plans in place to protect the species from extinction.

Professor Lymbery said part of the problem was that invertebrates, such as mussels, attracted less attention from the public and conservation agencies than larger, more charismatic animals.

“Carter’s freshwater mussel may not be as iconic or visible as species that command a lot of conservation attention, like numbats, whales and cockatoos, but they are vital to the health of our rivers,” Professor Lymbery said.

“If we lose this mussel, then the way our freshwater ecosystems function will be changed dramatically. Perhaps it’s about time we started to focus more conservation attention on invertebrates.”

Professor Lymbery said a number of actions can help prevent the extinction, including identifying remaining viable populations, protecting the habitat there and creating insurance populations.

“One of the reasons we have been so slow to realise the extent of the problem is that mussels are very long-lived,” Professor Lymbery said.

“Although existing populations are often quite large, many of these mussels may be 50 to 60 years old and will soon be dying out naturally.

“It may be possible to augment these existing populations with new generations or even replace populations that have been lost by releasing mussels bred in captivity, which is something that is done quite regularly in other parts of the world, such as the United States.”