Aquaculture for all

Shellfish restoration shown to improve Port Adelaide's ecosystem

Water quality Oysters Biodiversity +5 more

Shellfish species – including native razorfish, flat oysters and feral pacific oysters – are creating strong ecosystem benefits within the Port River estuary ecosystem in Adelaide, according to the results of a new study by Flinders University.

a shoal of fish near the seafloor
Juvenile whiting are more common in areas with shellfish reefs

© Brad Martin, Flinders University

Environmental monitoring of Port Adelaide, has shown many changes in water quality and species composition over the years. This led Flinders University PhD candidate, Brad Martin, to conduct fieldwork of the different shellfish reefs throughout the Port River earlier this year, to assess the species using these habitats.

Following the outbreak of disease in feral oysters, the South Australian Government introduced bans on collecting shellfish – including oysters, mussels and razorfish in the Port River in 2018 – around the same time, local community groups also began native flat oyster restoration projects, with native shellfish reefs once common to Australia’s coastline.

As well as finding high numbers of native fishes and invertebrates, the fieldwork also found several invasive species using the feral oyster habitat, including the first detection of Hercules club whelk (Pyrazus ebeninus), which was likely introduced through the ballast water from a shipping vessel.

“At present these intertidal species are unlikely to have significant negative impacts on other species, but could in spread in future beyond the Port River,” he said in a press release.

“The establishment of species from the east coast like the mud whelk and Sydney cockles is also an indication of warmer conditions. Until recently, these species only appeared in the SA [South Australian] fossil record and had died out during one of the previous ice ages.”

Martin said that the benefits of more shellfish in the area include improved water quality and provision of habitat and nursery grounds for other species, including important ones for recreational anglers – like whiting, bream and blue swimmer crabs.

Martin’s research work recently won the Fisheries Research Development Corporation (FRDC) Prize for Best Oral Presentation at the Australian Marine Sciences Association conference on the Gold Coast.

His supervisor Dr Ryan Baring also presented on ‘sediment stabilisation of the restored shellfish reefs,’ from research conducted on the Glenelg shellfish reef, with associate professor Graziela Miot da Silva, who is also from Flinders University.

In the two years since construction, Dr Baring says oysters are now growing on the restored Glenelg shellfish reef.

“The restored Glenelg shellfish reef has lots of oysters growing that are contributing to an ecologically important nutrient sink on the seafloor, which is important for turning bad nutrients from stormwater runoff into useful nitrogen in the sea and atmosphere,” he said.

“We have also identified a reliable hydrodynamic and sediment model to performance check and fine-tune the Glenelg Shellfish Reef to improve its ability to stabilise sediments that are extremely challenging to manage along highly developed metropolitan coastlines under climate change,” he added.

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