Balance needed between fishing and ecosystem function
August 7th, 2009 by cdunaganA widely publicized story last week about over-fishing focused on how two research advocates worked together on a study that concluded how fisheries could be made ecologically sustainable.
Boris Worm, a Canadian marine ecologist, previously took the position that commercial fisheries were likely to be wiped out in 40 years.
Ray Hilborn, a University of Washington biologist, called such conclusions nonsense, because he knew of fisheries that were doing quite well.
The two ended up debating each other together on National Public Radio and then decided to work together on a paper examining abundance of fish stocks. The paper, published last week in the journal Science, listed 21 authors.
Sandi Doughton of the Seattle Times does a nice job explaining the outcome of the study, as does Cornelia Dean of the New York Times and Richard Harris of NPR’s All Things Considered.
But it seems to me that, despite the collaboration, the result was that Hilborn was generally right when he criticized Worm’s position. Worm now seems to support the sustainable fisheries measures that Hilborn has promoted. (Review a video of a Hilborn lecture from May of 2006.)
The study is important because it calls for a new approach to fisheries management in place of the “maximum sustained yield” formulas that traditionally drove fishing levels. In truth, fisheries managers have been shifting their thinking for years.
To obtain maximum sustained yields, commercial fishers are allowed to increase the exploitation (harvest) rates to levels not generally good for optimum ecological function. In other words, removing large proportions of a target species may disrupt the natural predator-prey balance.
According to Hilborn, one can better protect natural systems and still have a “pretty good” harvest by settling for an exploitation rate lower than demanded by maximum sustained yield.
The next challenge will be to develop methods to calculate the proper balance between ecological function and harvests to feed the world.
The key message coming out of this new study is to actually look at how ecosystems are functioning — not just the success of the fisheries themselves.
Scripps Interactive Newspapers Group
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