By Mary Milliken

RIO DE JANEIRO (Reuters) - First-time Olympian Catherine Skinner of Australia battled to the end of a tense all-Oceania final in women's trap shooting to win the gold medal on Sunday, edging out Natalie Rooney of New Zealand by one shot.

The 26-year-old Skinner hit 12 of her 15 orange targets with her shotgun to Rooney's 11, but she got off to a rough start by missing the first target.

"I have had plenty of finals when I missed the first shot and it went downhill from there," said Skinner, who won her first gold medal in a major international competition.

After qualifying at the bottom of the six finalists, Skinner was a steady shot in the semi-finals blasting 14 of the 15 targets and went straight to the final, prevailing over a veteran field including defending Olympic champion Jessica Rossi.

Rooney, also a first-time Olympian, made it to the final in a shoot-off with American Corey Cogdell.

Cogdell, a three-time Olympian, took her second Olympic bronze medal by besting Spain's Fatima Galvez in a shoot-off, after each woman shot 13 of their 15 targets for the medal.

Skinner said having a fellow Oceania competitor next to her in the final was a big advantage.

"It is really relaxing seeing a familiar face there," Skinner said of Rooney. "I am glad she was there. I am so happy she got a result too."

Skinner's win gives Australia the lead among all countries in the ranking of gold medals, with three: one in shooting and two in swimming.

Taking up shooting at the age of 12 and competing since 2006, Skinner said her first Olympic memory was looking at the Atlanta Games medal tally and thinking "Shooting? Who does shooting?"

Now, the recently graduated chemical engineer said she views trap shooting as a "nerve-wracking" sport, making Sunday's breakthrough a big reward for the stress of the last six months.

Italy's Rossi crashed out in the semi-finals after missing five of the 15 targets, a big disappointment for the police officer after she easily claimed gold and set a world record in London 2012. She finished sixth.

World No. 1 Ray Bassil of Lebanon did not qualify for the final, finishing in 14th position.

(Reporting by Mary Milliken; Editing by Bill Rigby)