Specialist biosecurity dive teams are on high alert this summer for an invasion of marine pests, with the Bay of Islands at the front line.
The Bay of Islands marina is the first point of entry for foreign boats coming to New Zealand with thousands of boats to be inspected as they arrive in the next few months.
Sophia Clark, the biosecurity manager for the Northland Regional Council, says marine pests can "extremely alter our natural environment".
"We've already seen this part of Auckland and Whangarei where Mediterranean fan worm has taken over whole areas growing on scallop beds," Ms Clark says.
Inspections will be carried out for boats heading down to Auckland through to the top of the South Island and may be transferring cargo domestically.
Vessels found to be carrying marine pests must be cleaned at the owner’s expense and the owner could be liable for a $500,000 fine.