A Whangarei man says new regional maritime rules aimed at preventing the spread of marine pests are punitive towards boat owners.

Craig Chapman, whose boat has been infected by Mediterranean fanworm twice in 10 months while moored at Parua Bay, said some owners are considering legal action against the Northland Regional Council.

He is angry at having to pay thousands of dollars to haul his boat out, get it antifouled and return it to its mooring only to have it reinfected within months - and then find he has to do it all over again.

Read more: Heavy fanworm infestation on Bay of Islands boat


"Boat owners can only expect to get just a few months' use of a boat before again receiving a notice telling us not to use the boat unless transporting it to a haul-out facility," Chapman said.

"It certainly makes boat ownership in the Whangarei Harbour untenable."

He said most boat owners use ablative antifoul, designed to release attached organisms and marine growth when the boat travels through the water.

"How many fanworm are dislodged on the trip down the harbour for a haul out?"

Council biosecurity manager Don McKenzie said many boat owners were on learning curves regarding risk reduction and limiting the spread of pests such as fanworm.

He said ablative antifoul was not the right product for boats that were not used regularly; the idea was to prevent fanworm sticking to hulls moored in infested waters, not shed it in clean areas.

"This should not be a new topic for boat owners because we've been dealing with this for four years. It does require a change in thinking and behaviour.

"Despite the disgruntlement of some people, the pro-active stance we have taken means 14 of Northland's 15 harbours are still fanworm free."

Whangarei was the only affected harbour, and only in backwater current areas such as Parua Bay and Marsden Cove.

But Chapman believes a few boaties were paying too much when the infestation had nothing to do with breaking the rules.

Thousands of pleasure boats would leave fanworm-riddled Auckland harbour and travel north in the upcoming holidays, he said.

The topic has rankled boaties throughout the region, who say they cannot prevent their boat hulls picking up pests when an estimated 2000-4000 boats visit Northland each year.

Most of those owners did not contribute to the council's $79.50 biosecurity charge on marina and other mooring owners, whereas local owners did and also, in Chapman's case, paid haul-out and other prevention costs up to twice a year.