Stubbs said on top of that directors at Simplicity worked on a pro bono basis so it was natural that they tended to rotate more than paid directorships.
"So we're very sad Kirsty has left, but totally understand why and she remains a great friend of Simplicity."
Salt Fund Management managing director Matt Goodson said Campbell had been the independent chair of its compliance committee for some time and had been "brilliant."
Campbell is the first independent board chair Salt will have and will sit alonside owners Goodson and Paul Harrison.
Goodson said it had always taken the view that any independent director would need to be able to question its decisions while also moving in the same direction.
"We are obviously very pleased to have her on board," he said.
Meanwhile Harbour Asset Management will also see changes this year after its head of fixed income Christian Hawkesby will move to the Reserve Bank as an assistant governor next month.
Harbour portfolio manager Mark Brown will take over as head of fixed income.