More than 200 people attended the Protecting the Sea on Our Doorstep event on Whitianga.
“Hauraki Gulf’s story is not a great one,” Hauraki Gulf Forum CEO Alex Rogers said.
Speaking to a packed crowd in Whitianga, he said the gulf was under significant pressure.
The 2020 State of our Gulf report, produced every three years, depicted a collapsed ecosystem due to overfishing, invasive fishing practices, marine dumping and sediment and nutrient runoff, he said.
Since 2000, snapper, tarakihi and crayfish have been at, or have fallen to, levels requiring action to actively rebuild stocks.
Scallop, mussel, crayfish and pāua populations have also been declining for decades.