Marine activists are alarmed at the number of recent unusual whale sightings and strandings, which have been happening around the same time as seismic testing.
The surveying is being carried out off New Zealand's east and west coasts, by companies in search of oil drilling locations.
"We're not saying that seismic testing may have caused [the strandings] but we say it's another factor that has been added in recently," Sea Shepherd NZ director Michael Lawry says.
Sea Shepherd NZ says there have been at least three whale strandings and two "unusual sightings" since December 24.
No autopsies have been carried out on the dead whales, and the group is calling on the Department of Conservation (DoC) to make them mandatory.
"[Seismic surveying is] a variable and therefore we need to follow what we believe is the best practice for our whales."
Seismic surveying in New Zealand is overseen by government agency New Zealand Petroleum and Minerals.
It established a code in 2006 to minimise disturbance of marine mammals during seismic surveys, it says.
The code requires independent, DoC-approved, qualified Marine Mammal Observers and Passive Acoustic Monitors on board seismic vessels at all times.
"A variety of studies have been reported in scientific literature over the years, but there are none that have been conclusive on exactly how seismic surveying affects marine mammals," it says.
"It's important to acknowledge that seismic surveying has not been directly linked to strandings or deaths."
Mr Lawry says the recent whale strandings are unusual because the types of whales affected are usually found in deep water.
- December 27: Shepherd's beaked whale stranded at Caroline Bay
- December 28: A 14m pygmy blue whale found washed up on South Taranaki beach
- December 30: A young, fully grown sperm whale stranded near Nelson.
- December 24: Arnoux beaked whales, Otago Peninsula
- December 29: A group of what is believed to be sperm whale or beaked whales was observed before the single stranding occurred.
Otago University's Dr Liz Slooten agrees that autopsies should be carried out on the mammals to find out if they've been impacted by the seismic testing.
"Those sperm whales, beaked whales and other deep diving whales that are foraging in canyon areas can be frightened to respond by swimming rapidly away from the noise into shallow waters," she says.