A new report suggests the quality of water in Northland's Kaipara Harbour is so poor, it is heading for ecological disaster.
The Integrated Kaipara Harbour Management Group report says key snapper and shellfish stocks are in serious decline because of overfishing, sedimentation and increased pressure on land from farming developments.
Kaipara Harbour is the country's largest enclosed harbour, covering 743 square kilometres and with more than 3000 kilometres of coastline.
The management group's project co-ordinator, Leane Makey, says 90% of the rivers in the catchment are polluted.
She says it is the future of snapper they're most concerned about because the harbour is a significant breeding ground.