Shares in Port of Tauranga jumped more than 2.5% after it gained a weekly shipping service at the expense of Auckland, which is currently wracked by industrial unrest.
The international shipping line, Maersk says its weekly Southern Star service will now call at Tauranga instead, though its Northern Star service will continue to use Auckland.
Ports of Auckland says the loss will cost it nearly $20 million in revenue per year, and is another blow in its battle for supremacy with Tauranga for the title of the country's top port.
Maersk says the industrial unrest at Auckland's port is the main reason for the switch, though not the only one.
Trade and marketing manager Dave Gulik says Maersk does not want to have to divert vessels around the country because it disrupts importers and exporters, as it was forced to do last week because of the industrial dispute.
Mr Gulik says the company believed that keeping the Northern Star operating out of Auckland and Tauranga, while moving the Southern Star to Tauranga would give their customers the most diverse export option.
He says the plan is for the Southern Star to remain in Tauranga until at least the middle of next year, when schedules will be looked at again.
Port of Tauranga's shares rose 26 cents to $10.07 each on Tuesday.