Farming Blue Mussels

Distribution

The blue mussel is found in the temperate waters of both the northern and southern hemispheres and grows best within a temperature range of 16-22^oC. As a result of this requirement, the range of the species in Western Australia is limited to areas south of Geraldton.

Wild mussels tend to occur in bays and estuaries which have elevated levels of nutrients from land runoff, causing an increase in phytoplankton (microscopic plants) which is the main food for the filter-feeding mussels.

A large population of blue mussels developed in Cockburn Sound during the 1970s and 1980s due to an increase in the nutrient levels in the area. However the significant reduction in nutrients since the mid-1980s has resulted in a decline in this wild population.

In Western Australia the major mussel farming area is Cockburn Sound, but commercial mussel farming has also been established in King George Sound and Warnbro Sound (Figure 1).

Habitat

Blue mussels occur naturally in marine environments on shallow sandy bottoms in large communities attached to one another, known as beds. Mussels also occur as dense aggregations attached to submerged or partially submerged structures, such as jetty pylons. They are shallow water organisms, occurring to a maximum depth of 10 metres, although they are most abundant at or near low tide level, where the food supply of phytoplankton is most concentrated.

Although mussels grow best in marine embayments, they will also colonise estuaries or river mouths. However, given that mussels do not tolerate freshwater for extended periods of time, growth rates in these areas can be variable and serious mortalities occur when these areas are subject to substantial fresh water runoff.