Indicators to support an ecosystem approach to fisheries

The mean trophic level of the species groups reported in Food and Agricultural Organization global fisheries statistics declined from 1950 to 1994. This reflects a gradual transition in landings from long-lived, high trophic level, piscivorous bottom fish toward short-lived, low trophic level invertebrates and planktivorous pelagic fish. This effect, also found to be occurring in inland fisheries, is most pronounced in the Northern Hemisphere. Fishing down food webs (that is, at lower trophic levels) leads at first to increasing catches, then to a phase transition associated with stagnating or declining catches. These results indicate that present exploitation patterns are unsustainable.

Managing most marine finfisheries to achieve optimum yields is an unattainable dream. Protecting these resources from serious depletion through precautionary management seems the only practical option. But even this is of limited application if we demand scientific data for each managed fishery. There are too few researchers to do the work and, in any event, such research would usually not be cost-effective. Thus, we need not merely precautionary management; we need data-less management.