Researchers from Macquarie University have been conducting a large-scale research project across NSW, assessing factors limiting re-establishment of ecologically important oyster reefs.

Because of the travel restrictions imposed by coronavirus, it became difficult for the Sydney-based researchers to do regular monitoring of field experiments. So, Shoalhaven Riverwatch agreed to collect data from the three sites in the Shoalhaven River estuary.

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Oysters once formed extensive reefs across coastal NSW. Historic overharvest of shellfish to crush the shells for lime to make mortar for building dwellings, coupled with more recent disease outbreaks and decline in water quality, have reduced oyster reefs to less than 10% of their former abundance.

This loss has diminished the maintenance of clean water through filtration, shoreline stabilisation and enhancement of local fisheries production.

The researchers from Macquarie University set up the field experiment some months ago to understand how environmental factors such as predation, salinity, temperature, affect the natural establishment of oyster reefs in estuaries along the coast of NSW.

The results of this research will be used to determine areas where restoration is more likely to be successful.

Shoalhaven Riverwatch had an onsite conference call to the team coordinator on May 6 to establish procedures to follow in the gathering of data, then proceeded to count the oyster spat on the three levels of blocks.

Volunteers found it interesting to see the differences between the caged and uncaged blocks as the small fish could not get to the spat in the caged blocks.

The spat was not prolific but the spawning season was nearly over when the blocks were set up after the last flood.

The Riverwatch members collecting the data were Peter Jirgens, Ian Bice and Bruce Walker.