What are shellfish reefs and where have they gone?
Shellfish reefs are complex, 3D living structures, made up of high densities of oysters, mussels and other shellfish. They play a similar ecological role to coral reefs, providing food, shelter and protection for a range of invertebrate and fish species, as well as helping to reduce coastal erosion and improve water clarity. Shellfish reefs occur in enclosed and nearshore coastal waters in both tropical and temperate regions across every state in Australia. Before the 20th century, shellfish reefs were common features of coastal systems and were an important food source for Indigenous Australians. Early maritime explorers, such as Cook, Flinders, Eyre and Vancouver, regularly referred to extensive shellfish reefs in voyage reports and journals. From early European settlement of Australia, vast quantities of oysters and mussels were harvested for food to support the growing colonies and as a source of lime for the construction of early roads and buildings. It is estimated that shellfish reefs were commercially harvested during the 1800s and early 1900s in more than 150 locations across Australia, but are now considered functionally extinct habitats, with only a handful of reefs remaining (Gillies et al. 2015).
Towards the recovery of shellfish reef habitats
The loss of shellfish reef habitat, in addition to the loss and degradation of other important marine habitats, greatly inhibits our ability to manage the health of coastal environments and to ensure they remain environmentally, economically and socially productive. Healthy habitats enable the processing of nutrients and sediments into cleaner waters and abundant fish, while also sequestering carbon and helping to mitigate coastal risks such as sea level rise. Rebuilding native shellfish reefs and other marine habitats is considered a job-intensive industry, with more than 17 full-time and part-time jobs created per $1 million spent (Edwards et al. 2013). Types of jobs generated from restoration include marine engineering, construction, science, recreational fishing, tourism and ecotourism. Shellfish reefs are also considered ‘fish factories’, supporting the growth and augmentation of recreationally and commercially important fish species, such as snapper (Pagrus auratus), yellowfin bream (Acanthopagrus australis) and King George whiting (Sillaginodes punctatus).
In 2014, Australia’s first shellfish reef restoration project was initiated in Port Phillip Bay, Victoria. Since then, several new shellfish reef restoration projects have been established across Australia, demonstrating the momentum and interest in recovering shellfish reef habitat. These include Oyster Harbour in Western Australia, Pumicestone Passage and Noosa River in Queensland, Georges River in New South Wales, and Gulf St Vincent in South Australia. Much of this early work has leveraged the success of large-scale, long-term shellfish reef restoration projects in the United States, such as in Chesapeake Bay. Efforts to recover shellfish reefs can be strengthened by forming partnerships and collaborations with groups that have complementary knowledge and experiences that can support restoration efforts and long-term community stewardship. Partnerships among the shellfish aquaculture industry, recreational fishers, Indigenous groups, government and not-for-profit groups are particularly well suited to providing the resources, knowledge and community ownership required to sustain large-scale restoration efforts.