Detalle de: Mapping the distribution of Funiculina quadrangularis sea pen fields under two bottom trawling scenarios for delineating restoration areas

The sea pen Funiculina quadrangularis is the most abundant species of Pennatulacean present on the trawlable grounds of the northern coast of Spain, where it forms sea pen fields. This habitat provides relevant ecosystem services, including shelter, nursery areas, and spawning grounds for demersal species. Sea pen fields are particularly vulnerable to physical impacts and are classified as Vulnerable Marine Ecosystems (VMEs), likely among the most affected by bottom trawling due to their distribution on muddy bottoms. In this study, the biomass distribution of F. quadrangularis was modelled using a two-step approach based on Generalized Additive Models (GAMs). Along with different environmental variables (depth, slope, sedimentological characteristics, and oceanographical data), trawling pressure was included as an explanatory variable. The models were used to predict the biomass distribution of F. quadrangularis under two scenarios: (1) using current trawling pressure values (realized scenario) and (2) replacing trawling values with zero (potential scenario without trawling). A biomass threshold based on species richness was applied to differentiate between the general presence of F. quadrangularis from sea pen field areas, allowing for the mapping of VME distribution under both scenarios. The study determines a statistically significant negative effect of trawling in both model steps (presence–absence and biomass), which markedly reduced the extent of sea pen fields in the realized distribution. In contrast, the no-trawling scenario predicted a wider potential distribution of this VME. Although results should be interpreted with caution, this study provides spatial predictions of realized and potential distributions of F. quadrangularis fields in the studied area, supports the definition of reference conditions for this VME in the study area, and offers a novel approach applicable to other VMEs and/or regions.