At least five North Island iwi will be severely impacted from new restrictions to protect endangered dolphins, and there are concerns the changes will undermine promises under the Treaty of Waitangi.
The new rules will see extensions to areas where set-netting and trawling is currently illegal from October.
There are only 63 Māui dolphins left in the world, and they can be found on the West Coast of the North Island.
Iwi Collective Partnership general manager Maru Samuels said he understood that they were an endangered species, but now livelihoods were on the line.
The partnership represents 20 iwi-owned fisheries companies.
"We have five iwi from down that area, from the Taranaki-Whanagui region, and they will all be affected," he said.
"Some of their quota can only be caught from their backyard, which is the very area now subject to these changes. They have their own people employed in this area, so it's a double-whammy unfortunately for them."
Māori had a long history of commercial fishing before Crown legislation slowly dispossessed them of their customary practices at sea.
To compensate Māori for that loss, the Crown agreed to give them 10 percent of all existing quota under the 1989 Māori Fisheries Act, and later gave Māori 20 percent of the commercial fishing quota for new species in a 1992 settlement.
But Māori fishing authority Te Ohu Kaimoana chief executive Dion Tuuta said new restrictions on the West Coast of the North Island, and other areas in the South Island, would clearly undermine the settlement.
"The consequence of removing the set-netting as a tool to catch a particular species of fish is that you lose access to that fish, therefore the asset that was returned to you as part of your Treaty settlement has now been taken away from you," he said.
And he said it wasn't just going to affect iwi surrounding the areas where the new restrictions will apply.
"Iwi are either affected directly by losing access to their fishing grounds, or they're affected by the potential movement of fishing effort from the West Coast over to the East Coast, for instance, putting more pressure on local stocks. So this has the potential to affect iwi all around the country."
Fisheries Minister Stuart Nash said he received thousands of submissions from people supporting efforts to save the vulnerable Māui and Hector Dolphins including from Māori.
He said he engaged extensively with Te Ohu Kaimoana, iwi and Māori fisherman during the process and he was confident the new restrictions did not impede on the settlement.
"The very strong advice I've got is that the changes actually do uphold the durability of the 1992 deed of settlement so I don't believe that this does in any way, shape or form water this down or certainly breach it."
Nash said he also set up a transition plan, including a payment to help fishermen take up new fishing methods and further financial support for those who would lose their job or business.
But Tuuta said the government needed to find new technology, or develop a clearer transition plan where fishing could continue in the affected areas in a safe way. He said if that didn't happen, jobs would go.
"There is a young Māori fisherman that I know, he's been fishing for 20 years and he will effectively receive no transition assistance. There's another young guy I know, again, the future of Māori fisheries, and these measures will put him out of business."
The government is yet to announce the details of a further support package.