Freshwater mussels of coastal NSW Freshwater mussels are large, brown-black bi-valved molluscs that live on the bottom of streams and lakes, sometimes in dense beds containing thousands of shells. Although similar in appearance to marine mussels, the two groups have been separated for at least 200 million years and have very different biology. NSW has eight species of freshwater mussels that live in coastal streams. The species of freshwater mussels found in Australia and New Guinea are unique to the region and are not found anywhere else in the world. Their closest relatives live in New Zealand and South America. Mussels are most likely to be found in the middle or lower sections of permanently flowing streams. However, floodplain mussels are an exception; they can be found in temporary creeks and ponds, including farm dams, and avoid strongly flowing rivers. The stability of the stream bed is critical for mussels and the best habitats provide protection from scouring flows. These places have dense streamside vegetation and lots of large woody debris or boulders in the channel to stabilise the streambed sediments and provide refuges in times of flood. This is why mussels are usually patchily distributed within a section of stream. Shade from streamside vegetation helps to stabilise water temperatures and ameliorate water quality by shielding the stream from the sun. Juvenile mussels spend the first few years of life within the stream bed so streambed stability and sediment quality are important determinants of juvenile habitat. Organic sediments and places where the stream bed is clogged with fine silt are unfavourable for juvenile mussels. Mussels live in stable environments and are sensitive to pollution so their presence indicates good conditions for other aquatic animals. They have a long life span and are sedentary, so when they disappear it is a warning that something is awry. Mussels filter large volumes of water to extract their food, removing nutrients, algae, bacteria and organic detritus from the water. Mussel waste products are food for other animals and they, in turn, are food for water rats and platypus. Freshwater mussels were an important source of food for Indigenous Australians. Middens containing large numbers of mussel shells are widespread alongside rivers and lakes. Aboriginals also used mussel shells as tools.
Posted on: Mon, 29 Dec 2014 12:03:21 +0000
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