Emergent global biogeography of marine fish food webs

Abstract

AbstractAimUnderstanding how fish food webs emerge from planktonic and benthic energy pathways that sustain them is an important challenge for predicting fisheries production under climate change and quantifying the role of fish in carbon and nutrient cycling. We examine if a trait‐based fish community model using the fish traits of maximum body weight and vertical habitat strategy can meet this challenge by globally representing fish food web diversity.LocationGlobal oceans.Time periodPredictions are representative of the early 1990s.Major taxa studiedMarine teleost fish.MethodsWe present a size‐ and trait‐based fish community model that explicitly resolves the dependence of fish on pelagic and benthic energy pathways to globally predict fish food web biogeography. The emergent food web structures are compared with regionally calibrated models in three different ecosystem types and used to estimate two fish ecosystem functions: potential fisheries production and benthic–pelagic coupling.ResultsVariations in pelagic–benthic energy pathways and seafloor depth drive the emergent biogeography of fish food webs from shelf systems to the open ocean, and across the global ocean. Most shelf regions have high benthic production, which favours demersal fish that feed on pelagic and benthic pathways. Continental slopes also show a coupling of benthic and pelagic pathways, sustained through vertically migrating and interacting mesopelagic and deep‐sea demersal fish. Open ocean fish communities are primarily structured around the pelagic pathway. Global model results compare favourably with data‐driven regional food web models, suggesting that maximum weight and vertical behaviour can capture large‐scale variations in food web structure.Main conclusionsMechanistically linking ocean productivity with upper trophic levels using a size‐ and trait‐based fish community model results in spatial variations in food web structure. Energy pathways vary with ocean productivity and seabed depth, thereby shaping the dominant traits and fish communities across ocean biomes.