Pipi beds in the Ngunguru estuary near Whangarei are facing a new threat - from Asian paddle crabs.
The beds are just starting to recover from a major die-back, after local Māori placed a rāhui on the beds, backed by the Ministry of Primary Industries.
But the shellfish are now under attack from the big, aggressive crabs.
Biosecurity manager for Northland Regional Council Don McKenzie said Asian paddle crabs were found in Auckland and Whangarei harbours, but had never been seen at Ngunguru until 2014.
"We (council staff) started trapping there just recently, and we think their numbers are pretty-well established now," he said.
"I don't think we can eradicate them but if the community started catching them we could keep them at manageable levels."
Mr McKenzie said the crabs might have been deliberately introduced, but it was more likely they arrived on the hull of a boat.
"They are good eating and we 'd like people to trap them and either eat them or use them for bait. "
Unlike the native paddle crab, the Asian variety could inflict a nasty wound and could easily deal to pipi, cockles and even young flounder, Mr McKenzie said.