If the Commerce Commission and the Overseas Investment Office grant clearance for the sale, Sealord would take control of the Christchurch-based Independent Fisheries business.
The sale would include a quota of 46,000 metric tonnes, two owned and one chartered deepwater factory fishing vessels, more than 500 staff and a cold storage facility.
Independent Fisheries had humble beginnings as a small fish and chip shop in the Christchurch suburb on Linwood, founded in 1956 by Howard Shadbolt.
Since then, under the management of the late Charles Shadbolt - Howard's son - and Mark Allison, it has grown into one of the country's major privately-owned fishing businesses.
"There are immediate synergies that Independent Fisheries and the Sealord Group of companies can utilise both internally and externally that will provide excellent opportunities for the existing staff, customers, and suppliers to grow with the Sealord Group.
"In practical terms this means streamlining catch plans, logistics and innovation, with an emphasis on loyal customer service, which has been the backbone of Independent Fisheries business since its establishment."
Sealord chief executive Doug Paulin said ownership of the Independent Fisheries business was an "incredibly unique" opportunity as acquisitions of this type and quality rarely came along in deepwater fishing.
"The business is an excellent fit for Sealord both operationally and culturally, Independent Fisheries has a strong family-based culture built over many years by the late Charles Shadbolt, who had a passion for looking after his people and the wider community, and I am confident that Sealord can continue this proud tradition.
"We look forward to welcoming Independent Fisheries employees to the Sealord whānau."
Sealord said the transaction would be the largest financial transaction in the seafood industry since the Sealord deal in 1992 which was part of the Māori Treaty Settlement.
"Māori have a strong affinity with the moana, kaimoana and fishing. The fisheries settlement allocating iwi ownership of quota, including through the purchase of 50 percent of Sealord, underpins that cultural value system. This transaction grows iwi quota ownership, enhancing our strong connection with the moana in Aotearoa."