Hundreds of years ago, the oceans off the coast of North America teemed with cod. A new analysis highlights just how few of the big fish remain. The findings indicate that the volume of cod on Nova Scotia's Scotian Shelf has dropped more than 90 percent since the 1850s.

Using daily fishing logs from the 1850s--which recorded the number of fish caught, their size and their location--together with a population modeling program, Andrew A. Rosenberg of the University of New Hampshire and his colleagues reconstructed the total biomass of cod that existed in the area at the time. The team calculated that there were 1.26 million metric tons of the fish on the Scotian Shelf in 1852, compared with less than 50,000 total metric tons--and just 3,000 metric tons from adult fish--today. "Despite stringent regulations for the last six to 10 years and a slight rebuilding of fish stocks, the best estimate of adult cod biomass on the Scotian Shelf today comprises a mere 38 percent of the catch brought home by 43 Beverly schooners in 1855," the scientists report.

The results may help inform policy decisions for commercial fisheries. "Managing the remnants of the ocean's resources is a critical issue worldwide, but evidence for what constitutes a healthy fish population remains controversial," the authors note. "As we attempt to rebuild these fisheries, our decisions should reflect real and realistic goals for management, not just recently observed catch levels." The report appears in the March issue of the journal Frontiers in Ecology.