Fishing Down Marine Food Webs

TLDR

The decline in trophic levels is most pronounced in the Northern Hemisphere, also observed in inland fisheries. Fishing down food webs initially increases catches but eventually causes a phase transition to stagnation or decline. Trophic levels of global fisheries have declined since 1950, shifting from long‑lived, high‑trophic‑level species to short‑lived, low‑trophic‑level invertebrates and pelagic fish, indicating unsustainable exploitation.

Abstract

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.