Four new tugs will be operated by Rivtow, a recently created subsidiary of Queensland shipping company Riverside Marine.

With the latest move, BHP Billiton has diversified its supply of services and broken the monopoly of Teekay Shipping Australia.

It comes only a few days after the world’s largest bulk export terminal posted a drop in iron ore shipments for November.

But year-on-year volumes are still significantly increased on the back of higher demand from China.

Until