Sydney, Feb 15 (IANS): Australia has lost almost all its crustacean reefs, the most threatened marine habitats in the country, from its coastline, according to a study released on Thursday.

The study, led by non-profit Nature Conservancy, was conducted in collaboration with 10 other Australian organisations, and found that 90 to 99 per cent of these reefs have disappeared, Efe news quoted a statement from James Cook University.

"We already knew shellfish reefs were in bad shape globally with 85 per cent of them lost or severely degraded," said Chris Gillies, Marine Manager at Nature Conservancy Australia.

"Our study confirms that the situation for these important marine habitats in Australia is even worse with less than 1 per cent of Flat Oyster (Ostrea angasi) and 10 per cent of Rock Oyster (Saccostrea) habitats remaining," he added.

Crustacean reefs are formed by the agglutination of bivalves such as oysters and mussels, which create, modify and maintain a habitat that can support several specie of fish and invertebrates, as well as protect the coastline.

Most of these ecosystems disappeared between the 19th and 20th centuries due to destructive fishing practices, deterioration of water quality, invasive species, disease outbreak and environmental changes.

The largest decline was found in the flat oyster population as out of the 118 reefs identified in historical records currently only one has been located in Georges Bay on the island of Tasmania.

Study co-author Ian McLeod, also from JCU, highlighted the fact that these reefs are more threatened than the Great Barrier Reef, the world's largest coral system located in northeastern Australia.

"While (the Great Barrier Reef) and other coral reefs are indeed under threat, it's the shellfish reefs that have really suffered the most. It's just that most of them disappeared before we were born so people aren't aware we've lost them," explained McLeod.