Global Patterns of Small Pelagic Fishes’ Diversity: Present and Future ^†

Many of highly productive mid-latitude marine ecosystems share a prominent aspect in the configuration of their biological community structures. They appear to have a ‘wasp-waist’ food web, whereby the bottom (planktonic trophic levels) and top (apex and near-apex levels) of the food chain have high species diversity, while intermediate trophic levels are occupied only by few small pelagic fishes (SPF). SPF population dynamics is strongly correlated with temperature fluctuations, and since average global sea surface temperatures are expected to increase up to 1–6 °C by 2100, this warming trend may dictate profound impacts on SPF distribution and abundance. In this study, we used an ensemble of 6 ecological niche models and 21 earth system models to project, for the first time, changes in SPF richness, catch potential and geographic range size (comprising 47 anchovies, 33 herrings and 23 sardine species) by the end-century, by using two extreme scenarios (RCP2.6 and 8.5). We then predicted the latitudinal shifts that major SPF species might undergo due to climate change. Finally, we discussed the ecological and economic impacts potentially induced by climatic change, linking the projections with the global trends in landings since 1950. Our results suggest major effects on fisheries worldwide and highlight the need for adopting precautionary management that can easily adapt to projected changes.