MOST of the time, electricity and water are a deadly mix.
So it seemed rather unusual when research technician Andrew Bruce held a metal rod connected to a battery pack and sent 600 volts of electricity into a small pond in Sydney's west.
Odd as it may seem, Mr Bruce and his team from Primary Industries NSW were using the practice of electro-fishing to capture endangered Macquarie perch living in the Little Wheeny Creek in Kurrajong.
When used in the correct way, electro-fishing is a valuable method for surveying endangered fish species, Mr Bruce said.
''Within about a metre of the anode there is an electric field that is strong enough to stun any fish, making them easy to capture without harming them,'' said Mr Bruce, who wears protective clothing in the water.
Macquarie perch, whose numbers have diminished due to poor water quality and predation from introduced species, such as the redfin perch, are found in the Hawkesbury Nepean catchment area, and further inland in the Murrumbidgee and Lachlan Rivers which run through central NSW.
Mr Bruce said although the two groups had evolved into distinct species after being separated for more than 600,000 years, they were still classified as one species.
''They are very different fish. The Hawkesbury fish are about half the size of the inland ones.''
The team are hoping to study the habitat needs of the Hawkesbury Macquarie perch and have the group confirmed as a separate species.
''All the work we've done has been based on the inland fish. We don't know anything about these eastern fish and what conditions they need to breed in,'' said Mr Bruce.
Paul Bennett, a co-ordinator with the Hawkesbury-Nepean Catchment Management Authority, said the Macquarie perch living in Little Wheeny Creek were the only population found outside protected Sydney catchment areas and national parklands and locals had spent many years restoring the vegetation around the banks of the creek.
''The landowners have really taken to this fish, and see it as an icon for what they are restoring here,'' he said.