Rebuilding shellfish populations: critical ecological features of our bays and estuaries – under-appreciated, lost and under threat

Shellfish reefs or ‘beds’ were once dominant ecological features of bays and estuaries around southern and eastern Australia, providing habitat and food for many species, binding sediments, filtering algae and transferring... [ view full abstract ]

Shellfish reefs or ‘beds’ were once dominant ecological features of bays and estuaries around southern and eastern Australia, providing habitat and food for many species, binding sediments, filtering algae and transferring nutrients into benthic production. Similar to many other regions of the world, the historic lack of appreciation of these functions (shellfish are more than just a food), along with the poor treatment of estuaries in general, has allowed the large-scale decline of shellfish populations. Over the last couple of decades, particularly in the U.S., recognition of the ecological role of shellfish reefs, their major historic declines and the ongoing threats and limitations to these habitats has stimulated a number of major community/government/industry based partnership programs aimed at their protection, enhancement and restoration. Shellfish reefs have now been defined as essential fish habitats in the U.S.

In Australia, progress in recognising the past extent and ecological importance of shellfish in our bays and estuaries has been slower, but is now growing. Port Phillip Bay is a classic example of the historic demise of shellfish – in this case the native flat oyster (Ostrea angasi) and the blue mussel (Mytilus edulis galloprovincialis). Over the past century it is thought that over 90% of the shellfish beds and reefs that once existed in the bay have now been lost. While processes likely responsible for the demise, such as dredge fishing, chemical pollution and poor water quality have been removed or greatly improved – the shellfish have not recovered. This presentation provides some history of Port Phillip Bay’s shellfish and their decline and how a new opportunity has arisen to see if we can’t help them to return. What will it take to return the lost shellfish of Port Phillip Bay before they are lost from living memory?