Former whalers will join Department of Conservation staff again this winter to survey humpback whales moving through Cook Strait.
DoC's annual Cook Strait Whale Survey, now in its sixth year, begins on Saturday and runs until July 11.
The survey assesses the recovery of humpback whales since commercial whaling endedin New Zealand in 1964.
It is timed to take place around the peak period for whales migrating north to South Pacific breeding grounds.
DoC Wellington conservancy marine ecologist Nadine Bott said last year's four-week survey recorded 37 humpback whales and four pygmy blue whales.
The public could help researchers by reporting sightings of whales in the Cook Strait area or travelling up the coast from Kaikoura.
Reports were already coming in of humpbacks being sighted in those areas in recent weeks, Mrs Bott said.
She said preliminary survey findings suggested the number of humpback whales migrating annually through the Cook Strait were only about 20 per cent of the numbers seen in 1960, based on records from the Tory Channel whaling station.
"This represents some recovery from 1963, when fewer than 20 were seen during the whole season," Mrs Bott said.
"But humpback whale numbers in Cook Strait appear to remain highly depleted despite more than 40 years of protection."
