Fisheries scientists say it may be possible to limit the spread of an invasive Australian sea squirt in the Far North.
Known as pyura, the squirt has invaded rock pools at more than 20 locations on both coasts of Tai Tokerau.
MAF is worried it will threaten food species like mussels and has been testing removal techniques.
A team of tangata whenua and fisheries officers are attacking at spots where mussel beds are at risk.
MAF says cutting the squirt off the rocks with paint-scrapers seems to work.
Bio-security surveillance manager Brendan Gould says there's little sign of re-invasion in places where the team got rid of pyura last year.
He says it will never be possible to eradicate the sea squirt entirely, but it looks as if it can be controlled in places where it's a threat to kaimoana.
Several days were spent in 2010 manually removing the sea squirts from rocks at the Bluff on Ninety Mile Beach.
A trial was also set up in Parengarenga harbour, where one area was treated and another was left, to compare results.