"Once a dominant species, the volume of cod on the Scotian Shelf has plunged 96 percent since the 1850s," the scientists at the University of New Hampshire said in the report published in the journal Frontiers in Ecology.

Just 16 of the pre-Civil War schooners, based in port of Beverly near Boston, would be needed to haul in all the adult cod now swimming on the Scotian Shelf, they said.

And the scientists said the findings may indicate that overfishing around the world in recent decades has slashed many other fish stocks even further below their historical peaks than commonly believed.

"People tend to look only at recent data when they are looking at rebuilding stocks," said Andy Rosenberg, dean at the College of Life Sciences and Agriculture at the University of New Hampshire and a leader of the report.

"But that ignores the historical data -- cod has been exploited for thousands of years," he told Reuters.

Debate about restoring fish stocks often focuses on revival to levels within living memory -- like the 1970s or 1980s, he said. But those levels may also be severely depleted from the era before a mechanisation of fishing.

1,000 FISH A DAY

Off Nova Scotia in June 1852, for instance, one crew of eight under skipper George Gould landed 1,000 cod using hand lines with two hooks apiece, the report said.

Within just a few years, a widening use of lines with hundreds of hooks curbed catches off Nova Scotia. Another captain, Gilbert Weston, wrote in his log that he caught just 130 cod on May 23, 1859, while using 1,000 hooks.

North Atlantic cod has since been overfished around the ocean -- by nations including the United States and Canada and Iceland, Norway, Britain and Russia. The cod has become a symbol of the decline of many commercial fish species.

"In parts of the world we're following the same path," Rosenberg said. At an Earth Summit in Johannesburg in 2002, nations promised "on an urgent basis and where possible by 2015, to maintain or restore depleted fish stocks."

A few fisheries have been fairly stable in recent years, like Alaska pollack.

"There have been a few success stories ... but in a historical perspective all of these populations are probably very low," said Jeff Bolster, assistant professor of history at the University of New Hampshire and a co-author of the report.