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.