Kirby's chief financial officer, C Andrew Smith, will be stepping down from his position effective 7 September, the company said.

Smith, who is going to another opportunity, had been finance head of the US' largest operator of tank barges for three years. Chief executive David Grzebinski will take his place until a replacement has been found.

"Andy has been a valuable contributor during his three years with Kirby, and we wish him all the best in his future endeavors," Grzebinski said.