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NEWPORT, Ore. - A new study has determined that right whales in the Southern Hemisphere were once more abundant than previously thought, making their full recovery from near-extinction another 50 to 100 years away.

An international team of scientists using a combination of catch records from 19th-century logbooks and modern computer modeling techniques concluded that as many as 40,000 right whales once inhabited the waters near New Zealand before whaling drove them to the brink of extinction. As few as 20 mature females were estimated to have survived into the beginning of the 20th century.

Results of the study are being published this week in the journal Royal Society Open Science.

"This is the first time we have been able to estimate the pre-whaling abundance for this population of right whales before they were nearly decimated," said Scott Baker, associate director of the Marine Mammal Institute at Oregon State University, and co-author on the study. "Only a handful of whales survived, and those were threatened again in the 1960s by illegal Soviet whaling.

"The waters around New Zealand have been depleted of right whales for nearly 200 years," added Baker, who works out of OSU's Hatfield Marine Science Center in Newport, Ore. "We have little idea of the ecological role they played prior to whaling, or how they may contribute to ecosystems changes as their population slowly recovers."

Baker and co-author Nathalie Patenaude initiated the decade-long study of the remnant New Zealand right whale population in 1995, in part because the region has one of the best historical catch records from whaling logbooks and other sources. Southern right whales were particularly vulnerable to exploitation because they are slow swimmers with strong fidelity to sheltered bays for calving, making them "predictable and easy targets," the authors note.

The term "right whale" was coined because they were so easy to hunt.

"Once we had a good idea about the likely range of catches, we could do a full reconstruction using current estimates of abundance and population increase to measure the population's trajectory through time and how large it was," said Jennifer Jackson, lead author on the paper. Jackson, a former post-doctoral fellow with Baker at Oregon State, is now with the British Antarctic Survey.

The researchers' analysis concluded that prior to whaling right whales were abundant in New Zealand waters, numbering about 28,000 to 33,000 individuals. If most of the right whales harvested in the southwest Pacific Ocean were New Zealand whales, the population rises to 47,000 whales.

"Put in context, the estimated size of the current New Zealand population is less than 12 percent of these numbers," Jackson said.

Catch records of whaling from the early 19th-century were patchy and required a bit of detective work, said Emma Carroll of St. Andrews University, also a co-author on the study.

"We went back through early colonial New Zealand historical records and whaling logbooks, and even had to cross-reference what ships had been seen where to get an understanding of the scale of operations during the winter in New Zealand," Carroll said.

Funding for the study was provided by the Royal Society of New Zealand, The Lenfest Ocean Program of the Pew Charitable Trust, Oregon State University's general research fund, and the New Zealand National Institute of Water and Atmospheric Research (NIWA).