418 Dive Log Australasia JUNE 2026.pdf

The Fox in the Henhouse: Is Aquaculture damaging the integrity of the Jervis Bay Marine Park ecosystem? By Rod Sleath F or over forty years, members of the Jervis Bay Divers Club have dived and ex plored the waters of Jervis Bay and it’s surrounds. Many of the Bay’s best known dive sites are on the Northeast side of the bay. Iconic sites in the docks area like Deco rock, Slot Cave, Double Decker Cave and the Inner Tubes come to mind. Sites that are prime examples of Jervis Bay’s clear waters, beautiful sponge gardens and prolific marine biodiversity. These are areas they thought were safe — protected by the legislative shield of the Jervis Bay Marine Park, and sitting within a sanctuary zone, the area of a marine park offered the highest level of protection.

But beneath the surface, a silent, invasive takeover is underway, and it has been invited in by the very people charged with protecting these waters. Meet the Invader Meet Mytilus galloprovincialis, commonly known as the Mediterranean mussel. Included on the International Union for the Conservation of Nature’s (IUCN’s) list of 100 of the world’s worst invasive species, this mollusc is a biological powerhouse. It grows rapidly, releases more spawn than any other blue mussel species, and possesses a hardy resistance to temperature and salinity changes. Most dangerously, it hybridises with the Australian indigenous species, Mytilus planulatus, threatening the native blue mussel with genetic extinction. Historically, Jervis Bay was not home to visually obvious populations of blue mussels. Decades of diving experience from Jervis Bay Divers Club members confirm this. Yet, since commercial mussel farming operations began in 2020, we have witnessed a dramatic shift. Shallow reefs in the north-east of Jervis Bay are being smothered with Mediterranean mussels. Today, extensive mussel coverage is appearing on reefs down-current from the mussel farm. From Pyramid Rock under Point Perpendicular to the sanctuary zones of the Northeast Bay, the ‘blue mussel tide’ is rising. In recent months divers are noticing mature populations forming on the southern side of the bay on mooring lines at The Nursery dive site, and on the underside of marker buoys at the regularly dived Dent Rock. It appears the mussels are slowly continuing their spread around the Bay. Protection or Promotion? The NSW Marine Estate Management Act 2014 states that the primary purpose of a marine park is to maintain “ecosystem integrity”. Furthermore, regulations strictly forbid bringing “exotic” (explicitly defined in the regulations as non-indigenous) species into these zones.

Despite this, the Department of Primary Industries (DPI) oversaw the establishment of a commercial farm for the invasive Mediterranean mussel right in the heart of the Jervis Bay Marine Park. Even more concerning is the lack of foresight. The DPI’s investigative studies into the farm’s viability allegedly failed to mention the risk of mussel spread. The only study to predict this outcome was an honours thesis from the University of Wollongong — a study supervised by the DPI’s own scientists. It seems the risk was known, yet the precautionary principle, the better-safe-than-sorry approach essential to conservation, was abandoned.

Above and below: The ‘harmless’ Mussel Farm

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DIVE LOG Australasia #418.June ‘ 26

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