Blue Mussels Husbandry and Health Status

In Western Australia, mudworms (Polydora spp) which bore into the shell of the mussel have been reported. These worms have been found in up to 20 per cent of bottom grown mussels in and about six per cent of longline cultured mussels. The mudworm bores into the shell and the mussel secretes a flexible layer or a blister to cover the point where the worm comes into contact with its flesh. The mudworm lives in this blister and accumulates mud and food particles. The tunnels built by the mudworm affect the aesthetic value of the shell and if the blister bursts, mud may be introduced into the mussel.

A microscopic parasite known as mussel egg disease (Steinhausia spp) occurs in Western Australian mussels every few years. This microsporidian parasite lives inside the eggs of some mussels and causes the mussel meat to have a lumpy appearance when cooked. Mussel egg disease may alter the look of the mussel and also may reduce the number of eggs released during spawning. Mussel egg disease has absolutely no effect on human health or the taste of the mussel.

Mussels are susceptible to predation by fish and growth can be slowed by competition for space with other organisms such as barnacles, tunicates, tube worms and bryozoans, which are also filter feeders and reduce the food available to mussels.

Mortality on long lines may result from a lack of food (phytoplankton), or mussels being physically removed from long lines by extreme wave action in more exposed locations.

Quality Assurance

In liaison with the shellfish industry, the WA Shellfish Quality Assurance Program (WASQAP) was established jointly by the Department of Fisheries and the Health Department of WA in 1991 to ensure the safety and quality of shellfish grown in WA waters.

The quality assurance program for the shellfish growing sites in Cockburn Sound and the Albany Harbours includes sampling of shellfish for the presence of faecal bacteria, algal biotoxins and heavy metals.

The quality assurance program is overseen by way of a tripartite Memorandum of Understanding between the Health Department, the Department of Fisheries and the Australian Quarantine and Inspection Service (AQIS). The main goal of the testing program is to ensure the quality of the mussel product being harvested for both the domestic and export market. The Health Department also conducts regular water sampling, independent of the Shellfish Sanitation Program and these results are used as additional information for the WASQAP.

Results obtained since the inception of the program demonstrate that the water quality in Cockburn Sound and Albany Harbours is safe for the growing of mussels and that the main growing areas meet the standards required for both export and the domestic market.

Informtation courtesy of the WA Department of Fisheries