Populations of Australian Murray River crayfish have plummeted, as the clearing of stream bank vegetation and sedimentation in alpine regions has reduced their preferred habitat.

With large white claws and a particularly spiny abdomen, Murray River crayfish (Euastacus armatus) are the second largest freshwater crayfish species in the world. Generally, alpine streams are hotspots for these crustaceans. 

However, new research from the Australian National University (ANU) found that alpine populations of Murray crayfish have decreased by as much as 90 percent in areas that have been swamped with sediment and now lack deeper pools with plenty of boulders and overhanging shade trees to hide under. 

"Murray crayfish have been in decline in lowland rivers such as the Murrumbidgee and Murray, so these mountain streams could be an important stronghold for this threatened species," said Mae Noble, one of the study researchers from ANU's Fenner School of Environment and Society, in a news release. 

The Murray River crayfish is endemic to Australia, where it plays a vital role in aquatic ecosystems. They primarily feed on small aquatic species including insect larvae, water snails and tadpoles, as well as plant material including roots. Conveniently, they clean up dead and decaying matter and provide food for many other species, too. 

"Given the right habitat, alpine streams can be hotspots for these iconic creatures," explained Chris Fulton, one of the study authors from the ANU Research School of Biology. "But they are very fussy with where they live, which makes them vulnerable to habitat loss." 

The Murray River crayfish is the most widespread of its genus, with populations present in New South Wales, South Australia, Victoria and Australian Capital Territory. They prefer fast-flowing, well-oxygenated waters of both small, upland streams and large lowland rivers. However, the key to their survival is the presence of woody debris and deep holes the crayfish can burrow under. 

Fulton and Noble, who is a nasters student at the Fenner School of Environment and Society, were able to get a close-up view of the crayfish's habitat by snorkeling in cold high-country streams. 

"Looking into their world, we found where they like to call home, and their remarkable personalities and curiosity for new things," Noble added. 

Their findings, recently published in the journal Aquatic Conservation: Marine and Freshwater Ecosystems, highlight ways in which conservationists can restore and protect mountain stream habitats to ensure the survival of the crayfish.