Farming Blue Mussels

Aquaculture Potential

While Western Australia's mussel production is minor relative to the world production, the local demand for fresh product favours local industries. If the industry was to expand several fold it may need to sell more processed product and experience competition from large volume producers such as New Zealand, which produces 65 000 tonnes of green mussels (Perna canaliculus) annually. These industries will suffer higher freight costs but are highly mechanised. There is also a significant potential for New Zealand farmers to begin farming blue mussels which would further increase competition for Western Australian farmers. Having noted these potential limitations, the local mussel industry has been very successful with establishing mussels as a very popular part of local seafood cuisine, particularly in highly popular chilli mussel dishes.

The blue mussel industry in Western Australia produced 679 tonnes of product in 1998/99 worth over $1.8 million. With the advent of new farming technology and the possibility of value adding of mussel product, it has been predicted that in the next few years this figure could increase substantially through increased production and profitability on existing mussel growing sites. See Cole (2000) for monthly production trends. A national profile of exports is provided by Brown et al. (1997) and a review of the economic viability of mussel farming in Australia has been produced by Treadwell, McKelvie and Maguire (1991). Note that this analysis is highly sensitive to the size of boat used.

Availability of Sites for Mussel Farming

Further expansion of the mussel farming industry in Western Australia is limited by the availability of suitable sites. In Western Australia very clean tropical water is carried south in the Leeuwin Current. This water provides an opportunity to farm mussels in a clean environment, however this water contains very low nutrient levels and hence little food for mussels. As a consequence, mussel farming is likely to be restricted to areas where nutrient levels are increased due to run-off carried from the land by rivers. However, these areas often coincide with areas where human activity is greatest, possibly leading to conflicts between user groups.

In a review of characteristics of successful bivalve culture sites worldwide, Saxby (2000) concluded that unless suspended non-algal organic matter concentrations were very high, suitable sites were characterised by a minimum chlorophyll-a concentration of 1 microgram per litre (1 milligram per cubic metre). In a review of chloropyll-a concentrations in Western Australia, Pearce et al. (2000) found that there are relatively few locations in southern Western Australia where these conditions are met consistently. There have been attempts made to reduce nutrient entry into specific waterways including Cockburn Sound and Princess Royal Harbour where high nutrient concentrations have favoured excessive algal growth. Clearly, the potential exists to reduce nutrient concentrations to a level where chlorophyll-a concentrations can be too low for successful bivalve culture.

A new 55-hectare site has been established in the southern part of Cockburn Sound but the total production from this Sound will be influenced both by the productivity of these new sites and the future of existing sites near the Kwinana Grain Terminal.