Maori advisers to the Environmental Protection Authority say plans to mine phosphate from the Chatham Rise would potentially affect fisheries and eco-tourism such as Whale Watch Kaikoura.
The authority's Maori Advisory Committee has released a draft report on the proposal for the scheme some 450km off the Canterbury coast.
The EPA supports submissions from runanga and tribal trusts, who fear mining could damage the habitat of particular fish species, such as ling, juvenile hoki, orange roughy and warehou.
The Maori Advisory Committee says if those fish are affected by the scooping up of phosphate from the sea floor, the value of the Treaty settlement fishing quota could drop and constrain tribal growth.
However, the EPA also acknowledges there is a possibility that Maori could make economic gains from the project.
It says the company making the mining application, Chatham Rock Phosphate, does not spell out how tangata whenua would benefit from any employment and support industries.
The committee says some thought needs to go into any impact on New Zealand's sustainability brand, because it is vital that seafood exporters can sell quality and environmental sustainable products.