Will there be fish in the ocean in 2050? To address this question, we made a data‐rich global assessment of how fish biomass has changed over the last hundred years. We built on more than 200 ecosystem models representing marine ecosystems throughout the world covering the period from 1880 to 2007, and all constructed based on the same approach. We used spatial modeling to distribute biomasses based on habitat preferences, ecology, and feeding conditions. We extracted over 68,000 estimates of fish biomass (for predatory and prey fishes, separately) distributed over time and space, and used multiple regression to predict biomass distributions. The regressions were highly significant and predict that the biomass of predatory fish in the world oceans has declined by two‐thirds over the last hundred years. This decline is accelerating, with 54% having taken place in the last 40 years. We also found that the biomass of prey fish has more than doubled over the last hundred years, likely as a consequence of predation release. Jointly, these findings allow us to predict that there will be fish in the ocean in 2050, but they will be mainly of small prey fish. Our study also addresses the controversy whether ‘fishing down the food web’ is a phenomenon actually occurring in nature or a sampling artifact due to catches not representing relative abundances in ecosystems. Our study strongly indicates that the impact of fisheries has caused fishing down the food web of ecosystem resources at the global level

This is a contribution from the Sea Around Us project, a scientific cooperation between the University of British Columbia and the Pew Environment Group. VC further acknowledges support from the Canadian National Science and Engineering Research Council, and from the Nippon Foundation and UBC joint program, Nereus – Predicting the Future Ocean. This is Nereus Contribution No. 1

19 pages, 6 figures, 4 tables

Peer reviewed