- HALIFAX (CP) -- An entire
marine ecosystem is being restructured because of the collapse of East
Coast fish stocks more than a decade ago and could make their recovery
nearly impossible, according to a unique study to be published Friday.
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- Researchers who looked at data over a 40-year period
found that the food chain in the North Atlantic has been significantly
altered with the disappearance of large species, such as cod, a finding
never seen before.
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- Ken Frank, a scientist who co-authored the report in
Science magazine, said the findings provide an unsettling picture of the
marine environment on the eastern Scotian Shelf and the future of once
robust stocks that might never recover.
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- "It is worrisome," Mr. Frank said in an interview
from his office in Halifax. "It kind of suggests that we're locked
into this alternate state right now and unless there is some kind of unusual
event, it may take quite some time for the cod domination to return."
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- He said the virtual disappearance of cod and other large
species, such as haddock, flounder and hake, led to what he calls a cascade
effect. That is, large predators declined dramatically, but the fish they
preyed on - herring, capelin, shrimp and snow crab - were allowed to thrive
and eventually underwent a population explosion.
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- Cod, which used to sit on the top of the food chain,
have now been replaced by smaller fish.
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- That also trickled down to the lowest members of the
marine food chain - zooplankton and algae - which are being depleted at
a faster rate because more and more fish are feeding on them. That has
also raised the fear that the smaller fish species could diminish the nutrients
they rely on.
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- "Their levels have now decreased because they're
being eaten heavily by the exploding group," said Mr. Frank, who works
for the Department of Fisheries and Oceans at the Bedford Institute of
Oceanography.
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- "It was always known that when you deplete a predator,
its prey will increase. But it was never suspected that this would cascade
or extend all the way down to the base of the food chain."
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- Scientists have also always known that the cascade effect
existed in other bodies of fresh water, but they have never been able to
prove until now that it could be found in the ocean.
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- The report raises concerns that the new environment will
slow, if not prevent, the return of cod stocks, once the economic lifeblood
of many fishing communities along the Atlantic coast. Fish that now dominate
the food chain are feasting on young cod and making their recovery nearly
impossible, Mr. Frank said.
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- The reshaping of the marine environment has benefited
some, though. Seals have more to feed on since they are not having to fight
for food with cod. And fishermen are landing lucrative catches of high-priced
shrimp and snow crab, which are more abundant.
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- But Mr. Frank said the mistakes made in the cod fishery
should not be repeated with the shellfish industry.
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- "The collapse of cod should serve as a lesson that
if you want to keep the populations sustainable you've got to have a conservation
ethic in mind," he said. "You've got to resist the temptation
to fish so heavily that the stock will deplete itself."
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- The research also indicates the phenomenon of cascading
might be found in other areas of the North Atlantic where cod has diminished.
Mr. Frank is exploring whether the food chain has been disrupted in the
Gulf of St. Lawrence, the Grand Banks and the Labrador Shelf.
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