DEBORAH SMITH July 14, 2012
WHEN Mark McGrouther was sampling the waters near Roseville Bridge for the first time last month he was astonished to find a seahorse swimming so far from the ocean.
''It was way up middle harbour, which is staggering,'' Mr McGrouther, a fish expert from the Australian Museum, said.
Since the 1850s, museum staff have been throwing their nets into the city's famous estuary and collecting the interesting creatures they find, with many surprises, even today.
Now the first comprehensive study of the more than 20,000 records of specimens from Sydney Harbour has been carried out by museum staff, revealing the extraordinary biodiversity of the urban waterway.
The new research shows that more than 3000 different species of marine creatures call the harbour home.
''From the surface it looks like a desert. But underneath, it's very different. It's a marine jewel,'' Mr McGrouther said.
Among the unusual animals found have been a new species of mantis shrimp that can strike its prey with a razor-sharp claw in five milliseconds, a new species of spiky scorpionfish, and a striped coral crab normally found in warmer climes.
Emma Johnston, the director of the Sydney Harbour research program for the Sydney Institute of Marine Science, said despite the harbour's importance, no systematic survey of its inhabitants has ever been conducted.
So the museum's database was searched to provide a ''baseline'' record of harbour fauna, against which any future changes due to climate change or pollution can be assessed.
A review of all the scientific studies of the waterway conducted by different researchers has been carried out. ''Our aim is to be a one-stop shop for information about Sydney Harbour,'' Associate Professor Johnston said. The SIMS Harbour Hike will be held on Father's Day, Sunday, September 2, to raise funds for the research and to help inform Sydneysiders about the natural wonders of their city, she said.
Of the museum's 20,400 harbour records, 55 per cent were molluscs, 21 per cent were fish, 14 per cent were crustaceans, 5 per cent were starfish and 5 per cent were seaworms.
For these five groups alone, 2860 species were identified.
Shane Ahyong, the museum's crustacean expert, said the study revealed that many areas of the harbour have never been sampled. ''There are literally lots of black holes we need to fill in.''
Dr Ahyong, who identified the new species of mantis shrimp in 1998, said he had been very surprised to find a relatively large, undiscovered animal in the city's backyard, where people had fished for hundreds of years.
These highly aggressive crustaceans with excellent eyesight, Erugosquilla grahami, look a bit like a cross between a lobster and a praying mantis.
The complex geography of the harbour is a key to its rich biodiversity. ''There are lots of nooks and crannies and underwater valleys which provide great habitat for invertebrates and fish,'' Dr Ahyong said.
He said the brown and white striped coral crabs, Charybdis feriata, often surprise people who come across them because of their striking appearance.
In 2001, two specimens of another new species - the Sydney scorpionfish, Scorpaenopsis insperatus - were collected near Mosman. A bizarre anglerfish with sponge-like bumps on its skin and red tips on its fins, has also been spotted near Camp Cove. Information about the 11-kilometre foreshore walk can be found at harbourhike.com.