THE incoming chief executive of Chi-X Australia believes the equity market operator has reached an inflection point in its developments that will see it take a rapidly growing slice of local share trades.

John Fildes, who will take up the post on Monday, says the incumbent operator, the Australian Securities Exchange, has fat earnings margins that are ripe for the taking as Chi-X looks to build on its presence in Australia.

"The key thing is that Chi-X has now reached an inflection point where they are regularly reporting 10 per cent of the trades," Mr Fildes told The Australian from his holiday house in Canada.

"That is the point at which markets in Europe and elsewhere very quickly built to 15 per cent, 20 per cent and more."

Mr Fildes, a former executive with Morgan Stanley, block trading specialist Instinet and most recently high frequency trading firm Getco, replaces Peter Fowler, who oversaw Chi-X's establishment in Australia and plans to retire on May 1.