Push to bring back Australia's lost oyster reefs

<i>This is one environmental progran that makes sense -- if the costs can be curtailed</i>

Australia's southern states had their own version of a Great Barrier Reef until it was erased almost entirely by the middle of last century.

Before European settlement, the flat oyster reef ecosystem that dominated southern waters lay like a wreath around the coastline in bays, inlets and harbours. But with the oyster beds harvested for food or broken up to be used in cement, these reefs were made functionally extinct.

Now scientists, recreational fishers, conservationists and local governments are calling for government funding to bring the reefs back. They say previous public investment in reef restoration has exceeded expectations and expanding it will be a cheap, quick and effective regional jobs stimulus.

What's more, bringing back an ecosystem from extinction to the point where it could regrow itself would be a world-first, James Cook University marine biologist Ian McLeod said.

"The reefs act as a catalyst for a new food chain … [they] support lots of fish and all sorts of marine life, seagrass, worms and crabs," Dr McLeod said.

"It's surprising how well things have been going" with the handful of installations already established, he said. Reefs have been rebuilt over recent years in places such as Victoria's Port Phillip Bay, South Australia's Gulf St Vincent, Western Australia's Oyster Harbour and Port Stephens in NSW.

Oysters, and the mussels that proliferate among them, cannot naturally recolonise without help. Since their natural habitat was removed, bays have silted over and they need a bedrock to cling on. However, it's an easy fix.

The only requirement is some quarried limestone, concrete or compressed old shells harvested from restaurants to serve as a bedrock, seeded with oyster sprat and dropped overboard.

The Nature Conservancy is leading the campaign for funding. With $100 million, 60 reefs – about a third of the natural range of shellfish reefs – could be brought back, generating 850 jobs in construction, fisheries and service industries, it said.

"The reefs come back like a miracle ecosystem and provide a huge environmental benefit," said Nature Conservancy Australia director Rich Gilmore.

"There's huge water quality benefits. Each oyster filters about 150 litres of water a day. And then there's the fish benefits too. One hectare of oyster reef can create 375 kilograms of fish a year."

Mr Gilmore said the pilot reef installations had met with "no community opposition, but have overwhelming community support".

Recreational Fishing Alliance of NSW president Stan Konstantaras said restoring oyster reefs was a "no-brainer".

"More habitat equals more fish," Mr Konstantaras said. "Places like Botany Bay have suffered huge amounts of habitat degradation … everywhere has been modified by development. Every estuary on the coast would benefit from having an oyster reef."

Dr McLeod said the world was at "peak oyster industry" when Australia was settled, with vast oyster industries in New York and London quickly harvesting all their native shellfish beds for food.

The same thing happened to Australia's flat oyster, which once flourished from Sydney to Tasmania and Perth, and the Sydney Rock oyster, which lives from around Noosa to Sydney. Limestone oyster reefs in bays and estuaries were also busted up and hauled ashore once Australia had exhausted its land-based limestone resources to make mortar and cement.

By the time the Second World War rolled around, the flat oyster reefs were gone.

<a href="https://www.smh.com.au/politics/federal/push-to-bring-back-australia-s-lost-oyster-reefs-20200529-p54xo6.html">SOURCE</a>