Multiple configurations and fluctuating trophic control in the Barents Sea food-web

Abstract

The Barents Sea is a subarctic shelf sea which has experienced major changes during the past decades. From ecological time-series, three different food-web configurations, reflecting successive shifts of dominance of pelagic fish, demersal fish, and zooplankton, as well as varying trophic control have been identified in the last decades. This covers a relatively short time-period as available ecological time-series are often relatively short. As we lack information for prior time-periods, we use a chance and necessity model to investigate if there are other possible configurations of the Barents Sea food-web than those observed in the ecological time-series, and if this food-web is characterized by a persistent trophic control. We perform food-web simulations using the Non-Deterministic Network Dynamic model (NDND) for the Barents Sea, identify food-web configurations and compare those to historical reconstructions of food-web dynamics. Biomass configurations fall into four major types and three trophic pathways. Reconstructed data match one of the major biomass configurations but is characterized by a different trophic pathway than most of the simulated configurations. The simulated biomass displays fluctuations between bottom-up and top-down trophic control over time rather than persistent trophic control. Our results show that the configurations we have reconstructed are strongly overlapping with our simulated configurations, though they represent only a subset of the possible configurations of the Barents Sea food-web.

Ecosystem approach to harvesting in the Arctic: Walking the tightrope between exploitation and conservation in the Barents Sea

“…Two key conclusions emerge from our study and other recent models. First, like Sivel et al ( 2021 ) we find that top-down predation pressure is a fundamental feature of the Barents Sea food web (Experiment 3). The surge in planktivorous fish abundance, especially capelin, in the 1970s (Johannesen et al 2012 ) may have had some environmental origins but the models indicate a primary cause being relaxation of predation pressure as a result of demersal fish depletion through over-fishing.…”

Spatial food webs in the Barents Sea: atlantification and the reorganization of the trophic structure

“…This pelagic-demersal interaction is quite plausible in the shallow Barents Sea with strong benthic-pelagic coupling. If haddock really plays an important role in wasp-waist control, harvesting control rule parameters might be considered also for this species in future simulations, beyond cod, the species representing the demersal fish community [68].…”

Combined effects of temperature and fishing mortality on the Barents Sea ecosystem stability

“…As in Sivel et al (2021), we have expressed harvesting of fish species (i.e., pelagic and demersal fish) using harvest control rules (HCR), which resemble current fishing regulations in the Barents Sea (Gullestad et al, 2014). In this study, we added harvesting of benthos and marine mammals.…”

“…First, ecological time series are often relatively short, typically less than 50 years (Evans et al, 2015; Lotze & Worm, 2009), and, second, ecological time series are not available for all species of ecosystems. Consequently, the variability of ecological time series only represents a fraction of the possible variability of marine ecosystems (Sivel et al, 2021). An alternative is to use numerical models to simulate ecosystem dynamics over multiple decades.…”