When asked if his leaving had anything to do with the investigation, Grubb said he had no further comment and hung up.
An independent review last year found the organisation had a bloated management structure and was perceived as an “old boys’ club”.
It made more than 35 recommendations, including halving the then number of Fish and Game councils from 12 to six.
Grubb was charged with chairing an implementation steering group, though it was later revealed he opposed some of the changes.
In a letter to councillors announcing his resignation, seen by RNZ, Grubb said he never aspired to be chairman or lead the review and admitted the “last 18 months has been tumultous [sic]”.
“We now have a set of proposals that if adopted will make Fish and Game a modern agile expertly led organisation that delivers for its licence holders,” he wrote.
Grubb was appointed in November 2020. The organisation’s former chief executive, Martin Taylor, quit a month later. Corina Jordan was appointed as replacement chief executive in August this year.
Fish and Game has been contacted for comment.