A sick crewman on a large fishing vessel offshore of the west coast will be airlifted to hospital.

The Rescue Coordination Centre NZ (RCCNZ) received a phone call at 10.10am from a fishing company advising that the ship, 30 miles offshore west of Hokitika, had a sick crew member onboard.

The onboard doctor advised the man needed hospital treatment.

RCCNZ tasked Garden City Helicopters to airlift the sick crewmen from the vessel and take him to Christchurch for treatment.

RCCNZ Search Mission Coordinator Dougal Cockerell said the weather conditions were good so the helicopter would have "no problem" winching the crew member off the vessel and airlifting him to hospital.