FEATURE ARTICLE
Fishing Down Aquatic Food Webs
Industrial fishing over the past half-century has noticeably depleted the topmost links in aquatic food chains
Daniel Pauly, Villy Christensen, Rainer Froese, Maria Palomares
Medium and Message
Our study has prompted many fisheries scientists to review the statistics they have collected over the years for places of interest to them so that they can judge whether these ecosystems are suffering from a decline in trophic level. Our approach offers them a new tool for assessing whether fishing in a particular region is sustainable. But the publication of our results also engendered considerable critique from some members of the fisheries community. We welcomed this scrutiny and have tried to provide others with the means to examine the foundation of our analysis and to test the procedures we used.
As part of this same effort, we maintain a site on the World Wide Web—Fishbase.org—to aid communication among interested fisheries scientists and managers. We have also taken full advantage of the internet to disseminate "Ecopath," software we developed for modeling the food webs of aquatic ecosystems and determining such important quantities as the trophic level of various components.
We thus find ourselves manipulating computer spreadsheets more often than we would sometimes like. Without such work, we could never have mounted our study of global trophic levels. But with today's inexpensive personal computers and powerful software tools, the exercise has become rather straightforward. Indeed, the time was ripe to combine decades of statistical information about yearly catches–the fodder of fisheries research—with the modeling of food webs, a branch of ecology that had now grown mature. We thus believe that the results of our investigation provide a robust assessment of the shifts taking place in many regions of the globe—and for the world as a whole. Documenting the systematic decline in trophic level exposes the immense influence that industrial-scale fishing has had on marine and freshwaters ecosystems.
Clearly, we have skipped lightly here over many of the details of individual fisheries in an effort to give a comprehensive overview. Yet we see much value in presenting such a broad summary, one that should raise awareness of the scope of the changes that have taken place in lakes, rivers, estuaries, coastal waters and the open ocean. Perhaps if more people accept this message, fewer will be lulled into thinking, with Lord Byron, that humankind's ruinous ways have marked only the earth.
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