Paradox of woes and the fishes

Despite dioxins, heavy metals, decades of degradation and development, Sydney Harbour's marine life is richer than in more pristine marine parks along the coast.

Startling new studies reveal the harbour is teeming with more and bigger fish than realised, raising questions about whether marine parks are the piscatorial panacea they're trumped up to be. "It's a wonderful paradox," says Associate Professor Emma Johnston, who co-led a series of studies by the UNSW Ecology and Toxicology Group, in conjunction with Dr Melinda Coleman, a senior research scientist at NSW Fisheries.

The biological surveys of NSW estuaries revealed larval fish are more abundant and diverse in heavily modified harbours and bays. As well, adult fish in Sydney Harbour, such as flounder and snapper, are often larger than in less-modified estuaries.

Sydney scored best in comparison with Port Hacking, Jervis Bay and Batemans Bay, the latter two of which feature significant marine parks. So the science is in! The researchers used baited underwater cameras to film and count fish. They also used nets to sample and weigh adult fish, as well as sampling invertebrate creatures in sediments.

"The whole food chain turned out to be more productive in Sydney Harbour," Professor Johnston says. "It is a naturally productive waterway anyway, but humans have added all those extra nutrients and all those extra structures for animals to inhabit - such as wharves, jetties, sea-walls and bridge pilings."

Still, anglers need to remember that commercial fishing was banned in the harbour in 2006 because of world-record levels of toxic contamination in sediments. Eating fish caught anywhere west of Sydney Harbour Bridge is still not recommended.

Meanwhile, the fishing is firing for big kingfish on the reefs. Bonito are about the central coast headlands, marlin have been seen cruising in close, and there are oodles of flathead on the drifts.

The king tides have made Hawkesbury fishing tough, but the backwaters have good flathead on lures. There have been kingfish in Pittwater, with small jewfish and blue swimmer crabs in the river before the tides. Big tailor are getting around Flint and Steel. Narrabeen Bait says the local beaches are yielding plenty of whiting on live worms, big Aussie salmon on pilchards and lures, and prawns up the back of the local lake.

Sydney Harbour has kingfish but they're not exactly snapping. Port Jackson has bonito, tailor and Aussie salmon. Try the early morning troll. Also, try the Port Hacking flats at high tide for whiting.

This story Paradox of woes and the fishes first appeared on The Sydney Morning Herald.