A Kaipara fisherman says his catch this year is down by almost half and he suspects pollution of the Kaipara Harbour is to blame.
Peter Yardley has been catching flounder and mullet in the harbour for decades and says he has never had such a poor season.
Mr Yardley says farmers around the Kaipara Harbour have done a lot of work to protect it by fencing and planting riparian boundaries.
However he says floods in the Northern Wairoa River are now more frequent, bringing with them sediment and pollution from farms as far upstream as the Hikurangi Swamp.
Mr Yardley says flounder and mullet, which depend on the inter-tidal zone, have been particularly affected with catch rates down 30 - 50%.
He says there was a big algal bloom on the mudflats during winter, and that may have hit species like crabs which the fish feed on.