Waikato Tainui and Ngati Kahungunu are entering a joint venture, with Tainui's fishing quota fished from Hawke's Bay.
Ngati Kahungunu has already decided to fish its own quota, purchasing a deep-sea fishing vessel for $3.5 million.
The joint venture is valued at $20m, with Tainui possibly investing in Ngati Kahungunu's new boat or others.
Tainui Holdings director Tuku Morgan made the announcement at the Taniwha Dragon Economic Summit in Hastings yesterday.
He said Tainui might invest in another jointly owned deep-sea boat with Ngati Kahungunu but the initial focus was crayfish.
Tainui also brought strong business skills to the joint venture with a proven track record, he said.
Its businesses include hotels - it is building its fourth - and it plans an inland container terminal near Hamilton.
He said the $20m figure was flexible.
"The specificities of the deal are the easy bit," he said.
The "stars weren't aligned" for an earlier joint venture but the two iwis were inextricably linked and they would build a prosperous inter-generational future together.
"We pride ourselves in getting good returns - if you look at our hotels they are a money-making machine. Our growth last year was 14 per cent.
"We are going to work with Kahungunu commercially and we are going to build prosperity together.
"From the King all the way down we are excited."
Kahungunu Asset Holding Company director Taine Randell said there were not enough boats in the New Zealand fishing industry so it bought the 34m Glomford in Norway. It was currently leaving Panama waters en route to New Zealand.
As well as catching its own fish it sought a "deeper" relationship with Hawke's Bay Seafoods, which has caught and processed Kahungunu's fishing quota.
A cloud hangs over Hawke's Bay Seafoods following a 2014 raid by several government agencies, from which serious charges could still be laid.
Ngati Kahungunu Iwi Incorporated chairman Ngahiwi Tomoana said an experienced crew for Glomford were being sourced through various iwi, from Australia and Papua New Guinea.
"At the moment we don't do deep sea but post April/May we will be out fishing," he said.