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Point of No Return By Natasha Loder

Check out Point of No Return by Natasha Loder in Conservation Magazines, This Week's Good Read.

point of no returnEvidence is mounting that fish populations won't necessarily recover even if overfishing stops. Fishing may be such a powerful evolutionary force that we are running up a Darwinian debt for future generations. To learn more, check out Point of No Return by Natasha Loder in Conservation Magazines, This Week's Good Read. Below are a few quotes from the article:

"What is most worrisome about these evolutionary changes is that all the evidence thus far suggests that they can happen very quickly in fish populations—this is not the stuff of geologic time. Many studies suggest that the selection pressures are large enough for substantial change to occur within decades—even though the heritability of the traits is not large."

"Jeffrey Hutchings of Dalhousie University in Canada also spelled out to the meeting the possible consequences of this kind of evolutionary change. By the early 1990s, the numbers of Atlantic cod had declined by 99.9 percent relative to their abundance in the early 1960s (4). New work suggests that evolutionary changes may have been a factor in this decline because, prior to their collapse, cod were rapidly shifting toward younger and smaller sizes. One study shows that, between 1980 and 1987, the age at which 50 percent of the females were mature had dropped from six to five years."

"What the researchers are getting at is the idea that, when a population collapses due to overfishing, it is not simply the numbers of fish taken but also the type of fish taken that might be important. And just as evolutionary changes may be relevant to the collapse of populations, they may also be significant factors in the speed with which a population can recover. Hutchings says that, based on data from Newfoundland’s and Labrador’s northern cod, models suggest that “comparatively modest” reductions in age and size at maturity can slow recovery by 25-30 percent and more than double the likelihood of further population decline."

For more information about harvest and its impacts on wild fish recovery, visit our Harvest Reform Campaign section.

This article was originally published in University of Washington's Conservation Magazine: Volume 6, Issue 3, pages 124–129, July 2005.

Image/Illustration © Jon Krause

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