He and other kaumātua believe part of the problem was overfishing and tangata whenua should be able to manage the takutai moana, or marine environment, as Māori did prior to the arrival of Europeans.
"There's a lot of these MPs, they've never dipped their big toe in the water," Rewi-Wetini said.
"Yet they get the say on the whole coast. They do not know... what goes on."
"It's over the last few decades that the power was taken away from the iwi and hapū," Kawhia resident Bevan Taylor said.
"That's when things have started to deteriorate.
"This is what actually kaumātua from all the marae up the coast are saying. We need to take things back and control it and maintain these fisheries ourselves.
"We Māori did it for centuries, they did really well at it, and they knew when to rest the fisheries," Taylor said.
It was not only overfishing which was concerning. Taylor said increasing numbers of geese and swans were an "epidemic".
"Between swans and the geese we have got approximately up to 3000-5000 of them in Aotea Harbour/Kawhia Harbour and all the little lakes around. They're multiplying."
Taylor said the geese were eating the flounder at astonishing rates too. Apparently a dissected swan was found to have more than 80 flounder inside it.
"Not only are the swans eating all the flounder stock," Taylor said. "They're eating the vegetation that feeds the fish and they soil everything.
"They're s****ing all over the pipi bank over there. All that stuff just leaching into the harbour certainly won't be doing any good."
Residents from nearby Aotea Harbour agreed.
"All these things that our tūpuna put in place to protect fisheries, ngahere," said Davis Apiti. "We're seeing all these things depleting. It needs to change."
The proposed rāhui would be up to 100m depth along the coastline from Raglan to Mokau.
"We'll do it three by three years, then we will look at it," Rewi-Wetini said.
The first stage would begin next month with a cull of geese while they're nesting. Under New Zealand law, Canadian geese were not protected and may be killed year-round.
In later stages, iwi leaders hoped for support from the Department of Conservation and the Ministry for Primary Industries.
Fisheries NZ inshore fisheries manager Steve Halley said it routinely checked fish stock levels and was open to discussing iwi concerns.
In response to a proposed rahui, he said, "It would be important to discuss the concerns in more detail before determining what sort of measures would be effective in addressing them. Fisheries New Zealand would like to talk through the concerns and possible next steps."
A Waikato Regional Council spokesperson said water quality was high in the harbour and estuaries it monitored between November 2015 and February 2016.
In a statement, the regional council said: "We want this to remain the case, and so money has been budgeted in our 2018-2028 Long-Term Plan for a Harbour Catchment Advisor role that will initially be focused in the west coast to complete the development of sub-catchment plans for three harbour catchments: Whaingaroa, Aotea and Kāwhia."
The regional council said it would continue monitoring and work with iwi, community and other agencies.
That was welcome news for iwi, who hoped to see changes made to help safeguard the harbour and kaimoana supplies for future generations.
"We all have got grandkids," Rewi-Wetini said. "We are coming to the end of our life and we have got to have something for them to live on, it can't carry on like this."
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