Operational biofouling targets for the ROPME Sea Area: species-resolved priorities for vessel lay-up biosecurity

Prolonged vessel lay-up allows fouling assemblages to accumulate before ships re-enter transport networks, creating an acute biosecurity hazard for the Regional Organization for the Protection of the Marine Environment (ROPME) Sea Area (RSA) and the ports it connects to. Preparedness requires biological targets, not vector and pathway information alone. Drawing on the validated RSA biosecurity baseline, we identify seven extant very high-priority benthic fouling species associated with shipping and port environments, and cross-check them against an independent metabarcoding and photographic survey of the Saudi Gulf coast. Eight baseline species were recovered by that survey, including three of the seven; two further species classified as horizon in the baseline were also detected, constituting new occurrence evidence requiring verification. We set these targets within a five-component species–vessel–port prioritisation and define its scope, limitation and refinement. Regional source-species baselines, kept responsive to independent records, are a prerequisite for species-targeted inspection and surveillance in the RSA.