The range of an endangered New Zealand seabird overlaps with trawl fishing activity more than conservationists previously realised.

The Westland petrel is one of the last few petrel species that remains on the mainland of New Zealand, and inhabits much of the same breeding range on the West Coast of the South Island as it did before humans arrived.

Today, Westland petrels are threatened by a range of predators, and us - the species is the 10th most at-risk species from the impacts of commercial fishing.

In a just-published study, the Museum of New Zealand Te Papa Tongarewa's Susan Waugh and her colleagues outfitted 73 petrels with GPS loggers over the course of four breeding seasons to track where they went during their foraging trips in the Tasman Sea.


Results showed the birds' core feeding areas were consistent from year to year, located within 250km of their breeding colonies and focused on highly productive areas where the seafloor is steeply sloped.

But these sites often overlapped with areas of significant trawl fishing activity, and the researchers found further study was needed to see whether this translated to birds being accidentally killed.

Earlier work found local marine productivity as measured by fishery catches was strongly correlated with adult survival - and years with a greater fish catch were also years of higher adult survival.

"Our work on Westland petrels started in 2010, with a desire to understand how this species was faring demographically, as well as the key influences on it," Waugh said.

"Our work highlights a key factor in the birds' ecology that has strong implications for conservation - these birds predictably use the same waters year in and year out, regardless of El Nino cycles, and they are therefore a great candidate for a marine protected area to create protection of their trophic relationships.

"We feel this Westland petrel foraging data will provide a high-quality information source to help define key areas for marine conservation that will also provide protection for a whole suite of species."

Christophe Barbraud, a French seabird conservation expert who wasn't involved in the study, said a remarkable aspect of the research was that it spanned six years, across a range of environmental conditions.

"Whatever the sex or the breeding stage considered, Westland petrels consistently foraged in the same core areas from year to year."