First Ever Estimate Of Cod
Fishery In 1850s By UNH Researchers Reveals 96 Percent Decline On
Study provides insight for officials
setting ecosystem goals, rebuilding fishery remnant
Contact: Erika Mantz
UNH Media Relations
March 2, 2005
Editor: Andy Rosenberg can be reached at firstname.lastname@example.org,
and Jeff Bolster can be reached at email@example.com.
High-resolution images are available for download at: http://www.coml.org/embargo/embargo5.htm.
DURHAM, N.H. — Once a dominant species, the volume of
cod on the Scotian Shelf, a rich fishing ground off the coast of
Nova Scotia, has plunged 96 percent since the 1850s, according to
an article in the March issue of Frontiers in Ecology by Census
of Marine Life researchers. In fact, just 16 small schooners of
the pre-Civil War era could hold all adult cod currently estimated
in the once-rich Scotian Shelf.
Census of Marine Life researchers, who include University of New
Hampshire researchers Andrew Rosenberg, professor of natural resources
in the Institute for the Study of Earth, Oceans and Space, and W.
Jeffrey Bolster, associate professor of history, announced the first-ever
estimate of cod levels in the 1850s, created using old schooner
catch records and observations, coupled with modern modeling tools.
They say their findings have profound implications for contemporary
policy makers trying to rebuild fishery “remnants” and
restore the marine ecosystem.
Roughly 1,000 scientists from more than 70 countries are involved
in the $1 billion Census of Marine Life, support for which comes
from government agencies concerned with science, environment, and
fisheries in a growing list of nations as well as from private foundations
and companies. For more information: www.coml.org.
“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 researchers said.
“As we attempt to rebuild these fisheries, our decisions should
reflect real and realistic goals for management, not just recently
observed catch levels.”
According to the article, the 150-year perspective challenges ‘conventional
wisdom’ as to what constitutes a rebuilt cod stock in a productive
In recent debates in New England over management of George’s
Bank and Gulf of Maine cod stocks, for example, many argued that
1980s stock levels should be considered fully rebuilt. However,
“this contradicted the evidence of basic cod biology, which
suggested that cod stocks would only be rebuilt at higher levels.
“Our historical analyses indicate that recent levels of biomass
and catch may grossly under-represent the productive potential of
commercially important species,” the researchers said.
The article also emphasizes the importance of understanding ecosystem
trends and determining baseline levels of marine species that existed
prior to the industrialization of fishing. To date, declines have
only been vaguely described for predatory fish species and complex
coral reef systems around the world.
To estimate long ago fish levels, researchers used 1850s New England
schooner records of daily catch locations and fleet activity on
the fishing grounds. Fishers then, using handlines, had “negligible
incentive to falsify records” and, combined with ancillary
documents, their logs “provide a solid, reliable basis for
Using a mathematical formula, the researchers estimate cod biomass
on the Scotian Shelf was 1.26 million metric tons in 1852, compared
with less than 50,000 metric tons today, the adults within which
represent 3,000 metric tons, or 6 percent. The study notes the estimate
of 1850 cod biomass is “quite conservative” as the old
fishing logs only record adult cod.
The estimated abundance of cod in 1850 is consistent with earlier
research led by fellow Census of Marine Life scientist Ransom Myers
that estimated how much cod could be sustained in the North Atlantic
“This has important implications for ecological models,”
the researchers said. “Either cod comprised a much larger
fraction of the total ecosystem biomass 150 years ago or the marine
ecosystem was far more productive then.
“An important, and often overlooked, scientific question raised
by our historical analyses is, where has all this productivity gone?
One obvious possibility is that other species are now far more productive
than they were 150 years ago, when biomass accumulated in stocks
of cod and other demersals (fish found on or near the seafloor)
that were previously dominant components of the ecosystem.
“Alternatively, the marine ecosystem may now be far less productive
than in the past, because of a variety of natural and anthropogenic
changes. Put directly, has exploitation and overexploitation fundamentally
altered the structure of the ecosystem and have primary ecosystem
goods and services been lost because of these changes? Thinking
historically about the role of human activity in marine ecosystems
opens up new data sources and promising avenues of inquiry that
may begin to address fundamental ecological questions about the
nature and magnitude of productivity. Stock rebuilding programs
should consider longer term, high biomass goals for full restoration.”