The Cockburn Sound environment
A UNIQUE ENVIRONMENT
Cockburn Sound is a sheltered marine embayment south of the Swan River mouth at Fremantle. It is 22km long and ranges from 15km wide in the north to 9km in the south with an area of about 124 square-kilometres. Its central basin is between 17-22m deep, flanked by the relatively steep slopes of the surrounding banks. Garden Island extends along the western side of the Sound providing protection from prevailing winds and ocean swells.
Both in terms of its depth and shelter from ocean swell, Cockburn Sound is unique along Perth’s metropolitan coast and for several hundred kilometres to the north and south. Its unique environment includes organic-rich silts that provides habitat for the Sound’s seagrass meadows. These meadows provide critical nursery habitat for many of the Sound’s species including snapper, crabs, squid, herring and whiting. The Sound also supports the only known spawning aggregation of pink snapper (pictured above) in the West Coast Bioregion (Kalbarri to Augusta) – so protecting the Sound’s environment is critical to supporting fish stocks in it and beyond.
The Sound is also an important foraging area for little penguins and a nursery and feeding area for bottlenose dolphins.
Are the Sound’s seagrass meadows in serious strife?
With the loss of 80 per cent of its seagrass meadows over recent decades – an area equivalent to more than 1,800 Optus Stadium ovals, it’s even more important that everything is done to not just preserve the existing seagrass meadows, but to restore them through initiatives like Seeds for Snapper. This is also why Save Cockburn Sound has serious concerns about the damaging impact of the Westport development – the dredging of a new shipping channel in particular will result in millions of tonnes of sand being displaced, which could smother large areas of seagrass effectively making them cactus.
Westport itself acknowledges that this is a big issue that needs to be addressed:
“Marine fauna in Cockburn Sound may be affected through impacts such as habitat loss associated with excavation and reclamation, dredging-related turbidity, and increased vessel movements. Certain fauna may be more vulnerable to different pressures at different stages of their life cycles, such as the larval stage. Further, impacts on fauna that form integral parts of the wider ecosystem and food web (such as forage fish eaten by numerous predators) can result in larger ecological consequences.”
Westport Future Port Recommendations May 2020.
Holding the powers-that-be to account to save our Sound
The State Government acknowledges the need to protect the special place that the Sound is and the unique marine habitat it depends on.
In its latest report, the Cockburn Sound Management Council, made up of a number of key stakeholders with a direct interest in the Sound and which reports to the Minister for the Environment, wrote:
“Cockburn Sound is of vital economic and social importance to the Western Australian community and supports significant environmental values. Ongoing protection of Cockburn Sound is an important priority for the Government of Western Australia (State Government) to ensure that it continues to support the multiple values for which it is renowned.” – State of Cockburn Sound Marine Area Report 2022, The Cockburn Sound Management Council
But talk is cheap and we need to hold the Government and all the powers-to-be to account to ensure they are true to their word in making the protection of Cockburn Sound a high priority.