Drivers of coastal ecosystem structure: Using fishing mortality, primary production and temperature to predict biomass distributions of ecosystems along the Norwegian Coast

Abstract

Coastal ecosystems constitute productive marine areas that provide valuable ecosystem services such as harvestable fish stocks and critical habitats for spawning. With increasing impacts of human activities and climate change on coastal ecosystems, more knowledge about what shapes their structure is needed to manage them sustainably. Ecosystem modeling in Ecopath with Ecosim (EwE) has been widely used to investigate how factors such as fishery, environmental drivers, and bioenergetics of ecosystem groups, can affect marine ecosystems. Other studies have utilized the space-for-time and time-for-space substitution approaches in ecological research to obtain knowledge about specific ecosystems based on similar ecosystems in other places. In this study, a new approach combined ecosystem modeling and time-for-space substitution with the goal of predicting the structure of adjacent ecosystems. Potential drivers of coastal ecosystem structure were studied by applying ordination analyses on relative biomass distributions of fish and invertebrates from existing Ecopath models in the Northeast Atlantic. Based on an environmental stair-step approach, a modified EwE model for the North Sea was used to predict biomasses of groups along the Norwegian Coast, where fishing mortality, primary production and temperature were used as drivers in Ecosim simulations, and temperature-dependent curves scaled the consumption rates for ecosystem groups. In the multivariate analysis, temperature constituted a key driver of ecosystem structure in the Northeast Atlantic, and fishing mortality of large cod and primary production also seemed to contribute. Northern Ecopath models were associated with cold-adapted groups including cod, haddock and capelin, whereas southern Ecopath models were associated with warm-adapted pelagic fish groups like mackerel. Furthermore, flatfish and sandeels were characteristic for the North Sea Ecopath model. With representative input data for fishery and environmental drivers, the modified North Sea EwE model could to some extent predict biomasses of groups along the Norwegian Coast, in various areas with lower temperature, lower primary production, and different fishing mortalities for functional groups. Predicted biomasses for selected functional groups showed variable correspondence to observed biomass patterns based on bottom trawl survey data from two time periods. In the latter time period from 2000 to 2024, predicted biomasses corresponded more closely to the observed biomasses, with along-coast biomass patterns that were realistic for warm-adapted groups and some cold-adapted groups. These findings demonstrate that re-use of data can give further knowledge about ecosystems and enable transferability of ecosystem models.