Quantification of trophic interactions in the Norwegian Sea pelagic food-web over multiple decades.

• Main Authors: Benjamin Planque, Aurélien Favreau, Bérengère Husson, Erik Mousing, Cecilie Hansen, Cecilie Broms, Ulf Lindstrøm, Elliot Sivel
• Format: Article in Journal/Newspaper
• Language: English
• Published: Zenodo 2021
• Subjects: Linear inverse modelling; herring; mackerel; blue whiting; copepods; krill; amphipods; Norwegian Sea; competition; Copepods
• Online Access: https://doi.org/10.5281/zenodo.5710848

Whileecosystem-based fisheries management calls forexplicitaccounting forinteractions between exploited populations and their environment,moving from single species to ecosystem-levelassessmentis asignificantchallenge.For many ecologically significant groups, data may be lacking, collected at inappropriate scales orbehighly uncertain.In this study, we aim to reconstructtrophic interactions in the Norwegian Sea pelagic food-web during the last three decades. For this purpose, we develop a food-webassessmentmodelcompatible with existing observations and knowledge.The modelisbased oninversemodellingand isdesigned to handle input observations and knowledgethat are uncertain.Weanalyse if thereconstructed food-web dynamicsare supportive of top-down or bottom-up controls on zooplankton and small pelagic fishand ofcompetition for resources between the three small pelagic species.Despite high uncertainties in the reconstructed dynamics, themodel results highlight thatinterannualvariations in thebiomass of herring, mackerel and blue whitingcanprimarilybe explainedbychanges inconsumptionrather than by predation or fishing.Variations in the biomass of copepods and krill were alsolinkedtovariations inconsumption,whilethepastdynamics of amphipods can beexplained by both consumption and predation.The model results provide little support for the hypothesised competition for resources between the three small pelagic species, despite their overlapping diets.We conclude thatit is unlikely that theassessment and management of these commercial stocksduring the last 30 yearswouldhavebenefitedfrom explicit incorporation of trophic interactions. This article is published and available at: https://doi.org/10.1093/icesjms/fsac111