For 500 years, the waters off Canada’s Newfoundland were among richest fishing grounds in the world. In just a matter of decades, though, the arrival of modern trawlers to the Grand Banks in the 1950s led to a marine desert by 1992. Catches of cod peaked in 1968 at 800,000 tons, plunged to 34,000 tons by 1974. They plunged even farther–to zero–less than 20 years later, when the fishery was closed indefinitely for lack of fish. Cod stocks in the area remained at less than 5% of their former level (in terms of biomass) for decades despite the moratorium.
Today, the Grand Banks is a defining example of fishery collapse and mismanagement. But Canadian researchers publishing in the journal Nature, have found evidence that it may also come to represent the ability of even devastated ecosystems to recover, although perhaps never in the same way as before. The study shows
that cod are now at 34% of their pre-collapse peak, and biomass of all
predatory fish is at more than 50% of pre-collapse levels. This
promising recovery has followed some wild oscillations of predators,
prey and plankton populations–prey fish alone rose by 900% in recent
years — as a new balance was being restored in the ecosystem.
“The changes have brought to mind the ‘Humpty Dumpty’ nursery rhyme,”
wrote Queen’s University’s Jonathan Fisher, one of the study’s authors,
by email. “The question now is…whether the system will regain its former
structure, or whether, as Humpty Dumpty warned, missing or damaged
components…may prevent the ecosystem from returning to its former
“The answer to the critical question of whether or not such profound changes in the dynamics of large marine ecosystems are reversible seems to be ‘yes,’” the study argues. Yet, though cod’s seemingly inevitable extinction has been reversed, the Grand Banks is not the same as before. New species, particularly haddock, sit atop the food web where cod once ruled, and the cod that have returned are much smaller than before. No one is sure what this will mean in the future.
Similar patterns have occurred in the North Sea, Black Sea and Baltic Sea where species recoveries have been delayed by new competitors, invasive species, water pollution, or continued overfishing. It may even be that under the best conditions such as the Grand Banks–a well-enforced fishing moratorium and an otherwise intact marine ecosystem–recovery will take many decades, and never be the same as before.
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