Bishop Anthony Fisher, 50, brought a message of charity and the importance of youth in the church to the audience at St Patrick's Cathedral.

``This is a young diocese, canonically and demographically,'' he said. ``By comparison to the median age of its people, in their early 30s, I'm already an old guy!''

He then directed comments at the younger members of the congregation.

``Examine your hearts now,'' he said. ``God is calling some of you to join the adventure of the gospel through the priesthood or consecrated life.''

Youth was the official focus of his appointment, the bishop said in an interview before the ordination.

``I think they wanted someone young and I'm the youngest bishop in Australia,'' he said of why he was chosen for the position. ``I was also involved with organising World Youth Day.''

But a careful listening to his homily detected an undertone of one of Fisher's strongest passions human life. ``I look forward to working with the leaders of our civil community and economy in support of the dignity of every human from conception to natural death.''

Later he added: ``My life has been and will be devoted to the defence and support of human life and love.''

The new bishop promised to visit every parish in his new diocese and say mass but admitted the process was a bit daunting.

``If I travel to a new parish every second Sunday it will take over two years to get around to them all!''