The forgotten shellfish reefs of coastal Victoria: documenting the loss of a marine ecosystem over 200 years since European settlement

Abstract

Victoria has lost vast areas (>95%) of native flat oyster (Ostrea angasi, Sowerby 1871) and blue mussel (Mytilus edulis galloprovinicialis, Lamarck 1819) reefs from estuarine and coastal waters since European settlement. We document the decline of these reefs by examining indigenous use of shellfish, the decimation of oyster reefs by dredge fishing in early colonial days (1840s–1860s) and later removal of mussel reefs by the mussel and scallop dredging industry (1960s‒1990s). Review of current scientific information reveals no notable areas of continuous oyster reef in Victoria and we consider this habitat to be functionally extinct. While the large-scale removal and destructive fishing practices that drove the rapid declines have not occurred since the mid-1990s, a natural recovery has not occurred. Recovery has likely been hampered historically by a host of factors, including water quality and sedimentation, lack of shell substrate for settlement, chemical pollution impacts, disease of native flat oysters (Bonamia), and more recently introduced species that compete with or prey on shellfish. However, research in the United States has demonstrated that, by strategic selection of appropriate sites and provision of suitable settlement substrates, outplanting of aquaculture-reared oysters and mussels can re-establish shellfish reefs. While a long-term sustained and structured approach is required, there is potential to re-establish shellfish reefs as a functioning ecological community in Victoria’s coastal environment.