Ngāi Tahu has had a long involvement in commercial fishing and runs a successful commercial seafood company, Ngāi Tahu Seafood, which supplies seafood products to domestic and international markets. Since allocation of the Māori Commercial Fisheries Settlement, Ngāi Tahu has strengthened and grown its commercial seafood enterprises. Most seafood offered by Ngāi Tahu Seafood is caught against Ngāi Tahu quota by Ngāi Tahu fishers – families who have been fishing for generations.

Sir Mark was elected Kaiwhakahaere of Ngāi Tahu in 1998. Of Ngāi Tahu and Ngāti Kuri descent, he currently holds directorships on Te Pātaka o Rauru, Te Pookai Aronui and Te Tapuae o Rehua. He is a Trustee for Pure Advantage and a Summit Member of the Hillary Institute.

He has served on numerous boards including the Museum of New Zealand Te Papa Tongarewa from 2001 – 2007, and was an original member of the Minister for Māori Affairs, the Hon Dr Pita Sharples’ Māori Economic Taskforce.