The Port of Tauranga says testing all foreign seafarers for Covid-19 is not practical and that no port workers would be a close contact with international seafarers while in port.
It comes after the Maritime Union called for testing of all seafarers entering New Zealand waters after a marine electronics engineer tested positive for the virus on Saturday after working on a ship while it was in Auckland.
The ship, called Sofrana Surville, had been identified as the most likely source of infection.
The Sofrana travelled from Brisbane to Tauranga and then to Auckland, where eight crew joined it from the Philippines. They were released from managed isolation on October 13 but had only flown into New Zealand a few days prior.
Eleven people were considered to be in contact with the Sofrana Surville while it was in Auckland.
Toi Te Ora was working to track people who boarded the same ship while it was in Tauranga for two days last week.
A Port of Tauranga spokeswoman told the Bay of Plenty Times it would "not be practical" for all international seafarers to be tested as many ships are often only in port for less than 24 hours.
"Both crew and port workers who need to go aboard visiting ships maintain physical distancing and wear full PPE including face masks and gloves. Crew members are not permitted shore leave unless they have been at sea for longer than two weeks and return a negative Covid-19 test."
She said virtually no port workers would meet the definition of a close contact for foreign seafarers.
Maritime Union national secretary Joe Fleetwood said they were calling for foreign seafarers to be tested before leaving each international port and upon arrival into New Zealand.
He compared the "gap in the system" as bringing a group of people over on airplanes, not testing them and then allowing them contact with members of the public, he said.
"It's really no different."
He said it was only a matter of time until a blunder at the coastal border would let Covid-19 back into New Zealand and it was important to "cover all bases" and single out "points of infection".
Fleetwood said it was "not enough" to just disallow foreign ship workers to come ashore as either way ports would be sending workers on board to work and unload cargo and then go home to their families.
He said it was a bit of a "mixed bag" on how port workers the union represented felt, with some feeling concern about the risk and others feeling okay as they were confident they could keep a sufficient distance from foreign crew.
"New Zealand has been very, very lucky, we don't want to ruin it all with some little gaps in the system."
The Maritime Union had approached the Government about the testing, as well as rallying to "limit the points of entry and infection", he said.
Their idea was to reduce international port entry from 16 to four, meaning only Auckland, Dunedin, Tauranga and Christchurch would take international cargo, he said.
"This would allow all four categories of cargo to still enter the country but limit the risk of the virus entering at a number of coastal entrances."
In response to this, the Port of Tauranga spokeswoman said Covid-19 protection was a "completely separate issue" and the "logistical challenges would be enormous and far outweigh the benefits".
"The management of the positive cases in the past few days show the system is working. Our economy relies on sea freight for both imports and exports and we need to ensure cargo can keep moving safely."
Meanwhile, New Zealand-based ship the Moana Chief, was moving to Tauranga today for all crew to be Covid-19 tested to rule out the ship as the source of Saturday's infection.
In a statement today, the Ministry of Health said it was unlikely to be the source.
There were no new community cases of Covid-19 today.
A Ministry of Health spokeswoman said it worked closely with Maritime NZ, Ministry of Transport and NZ Customs, on how to prevent Covid-19 from entering New Zealand across the maritime border.
She said mandatory testing was in place for seafarers returning home permanently or for shore leave.
"For seafarers who are working on or around vessels, and for workers encountering seafarers on other vessels, there are good measures and advice in place for these workers to follow including eliminating the need to be on the vessel or near crew, keeping necessary time on the vessel to a minimum, practicing good hygiene, social distancing and the use of PPE."
She said regular mandatory testing of higher-risk port workers was also in place.
The Ministry regularly refined the testing programme to ensure that it remained fit for purpose for its elimination strategy, she said.