Ocean · food
Fishing down the food web
Definition
Fishing down the food web describes the tendency of industrial fisheries to deplete large, high-trophic-level species — tuna, cod, groupers, sharks — and then compensate by targeting progressively smaller, shorter-lived species at lower trophic levels, such as sardines, anchovies and invertebrates. The concept was documented by Daniel Pauly and colleagues in the late 1990s ("Fishing Down Aquatic Food Webs"), who showed that the mean trophic level of global landings had declined as top predators were fished out. The trend signals serial depletion masked by apparently stable total catches.
References
industrial fishing depleting top trophic levels, documented shift to lower-trophic species
Overview
What it means
Because low-trophic species are also the forage base for predators, seabirds and marine mammals, fishing down the web risks restructuring entire ecosystems; it also underpins the aquaculture feed question, since much low-trophic catch becomes fishmeal and oil rather than food.
How it is used
Used in fisheries science, marine-conservation advocacy and ecosystem-based management debates; tracked via mean-trophic-level indicators of catch.
Why it matters
It reframes overfishing from a single-stock problem to a food-web problem, motivating ecosystem-based quotas and protection of forage species.