By 3 News online staff
A survey of humpback whales in the Cook Strait has recorded the highest number in more than a decade, which has excited and "exhilarated" those undertaking it.
The annual four-week Department of Conservation survey in partnership with OMV New Zealand, ended on Saturday, with 137 whales spotted – the most since the count began in 2004.
The record for the most whales seen in a day was also broken, with 27 seen on June 21.
This year's survey also threw up a few surprises, with a rare white humpback thought to be the well-known whale Migaloo which normally migrates through Australia.
A newborn humpback was also seen for only the second reported time in New Zealand waters, while the survey team also saw blue and sperm whales.
Survey leader Nadine Bott believes the increasing numbers show New Zealand's whale population is on the increase, but not as much as Australia.
"We are not yet seeing the extraordinary rates of increase they have in Australia of around 11 percent a year. Perhaps that is something we will enjoy in our waters in the future," she says.
Volunteers, including six former whalers, lead the whale spotting from a high point on Arapawa Island which overlooks the Cook Strait.
Once whales are located, a boat heads out to collect photos and also skin samples using a biopsy dart to identify individuals.
DNA testing showed four humpbacks have been seen twice during the 12 years of the survey.
However, during the survey, two humpbacks were seen with craypot lines caught on them with line and buoys trailing behind.
They weren't able to be freed by DOC staff because they were moving too fast.
The recovery of humpback whales is compared to whalers' records in the Cook Strait in the 1950s to early 1960s.
Whale survey numbers:
(2004 to 2007 surveys ran over two weeks)
(2008 onwards increased to four weeks with OMV NZ sponsorship)