Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

First ever estimate of cod fishery in 1850s reveals 96% decline on Scotian Shelf

02.03.2005


New insight for officials setting ecosystem goals, rebuilding fishery remnant

Once a dominant species, the volume of cod on the Scotian Shelf has plunged 96% since the 1850s, according to landmark research published today. 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.

Writing in today’s edition of Frontier’s in Ecology (www.frontiersinecology.org), Census of Marine Life researchers announced the first-ever estimate of cod levels in the 1850s, created using old schooner catch records and observations, coupled with modern modeling tools. And they say their findings have profound implications for contemporary policy makers trying to rebuild fishery "remnants" and restore the marine ecosystem. "Managing the remnants of the ocean’s resources is a critical issue worldwide, but evidence for what constitutes a healthy fish population remains controversial. As we attempt to rebuild these fisheries, our decisions should reflect real and realistic goals for management, not just recently observed catch levels."



150-year perspective challenges ’conventional wisdom’

The researchers say that a 150-year perspective challenges ’conventional wisdom’ as to what constitutes a rebuilt cod stock in a productive marine environment. 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 emphasize 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 stock assessment."

Changing fishing patterns suggest handline fishery in sailing schooners depleted regional cod stocks. Between 1852 and 1857, Beverly vessels fished the Scotian Shelf close to 90% of the time, a figure that declined to 60% in 1859 as captains searched farther afield for more economically profitable concentrations of cod. Some vessels left the Beverly fleet and may have left the cod fishery altogether, a familiar pattern in collapsing fisheries today. Catch per unit of fishing effort (CPUE in fish per day per ton of vessel) declined by over 50% between 1852 and 1859. "In the logs themselves, effort was measured in a good day’s catch. On May 23, 1859, Gilbert Weston, captain of the Dorado on the Scotian Shelf’s Banquereau Bank, noted in his log that they ’had 1000 hooks out (on trawls) and (caught) 130 (cod) fish.’ However, men who had fished in 1852 remembered good days when seven or eight handliners fishing two hooks apiece over the schooner’s rail could each bring in more than 100 fish. George Gould’s crew of eight on the Betsy & Eliza had four such good days in 1852, landing more than 1,000 cod on one long day in June."

Estimated 1.26 metric tons of cod on Scotian Shelf in 1852

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%.

The study notes the estimate of 1850 cod biomass is "quite conservative" as the old fishing logs only record adult cod. "Prevalent hook sizes in this deepwater fishery made landing smaller juvenile cod very unlikely." "Despite stringent regulations for the last 6–10 years and a slight rebuilding of fish stocks, the best estimate of adult cod biomass on the Scotian Shelf today comprises a mere 38% of the catch brought home by 43 Beverly schooners in 1855. In other words, 16 small schooners from this mid 19th century fleet could contain all of the adult cod on the Scotian Shelf today."

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 ecosystem. "Biomasses for many key marine species that are also valuable economic commodities probably follow the pattern we have estimated for this cod population." the authors say. "That is, biomass of commercially important species today is only a small fraction of what existed before industrialized exploitation." Other researchers using entirely different types of data and methods recently showed similar levels of depletion for North Sea fish stocks.

Where has productivity gone?

"This has important implications for ecological models. 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."

Terry Collins | EurekAlert!
Further information:
http://www.coml.org
http://www.frontiersinecology.org
http://www.hmapcoml.org

More articles from Ecology, The Environment and Conservation:

nachricht A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde

nachricht Value from wastewater
16.08.2017 | Hochschule Landshut

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Cholesterol-lowering drugs may fight infectious disease

22.08.2017 | Health and Medicine

Meter-sized single-crystal graphene growth becomes possible

22.08.2017 | Materials Sciences

Repairing damaged hearts with self-healing heart cells

22.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>