Ships laid up in and around the Strait of Hormuz since February present a documented biosecurity concern as maritime traffic resumes. Research indicates more than 1,500 commercial vessels anchored in the Persian/Arabian Gulf have likely accumulated substantial marine biofouling—plants, invertebrates, parasites and microbes—on hulls and niche areas. When these vessels depart, they can transport organisms to new coastal regions, with potential impacts on native ecosystems, fisheries, aquaculture and coastal infrastructure.
Maritime trade depends on a small number of critical choke points; only a few, including the Strait of Hormuz, lack viable alternative routes. Historical precedents such as large-scale layups during the 2008 downturn and earlier oil crises, and the temporary mooring of cruise ships during the COVID-19 pandemic, show how idle vessels can become vectors for biological transfer. The Persian/Arabian Gulf is already home to more than 50 non-native marine species, increasing the likelihood that vessels leaving the region could carry potentially invasive organisms.
Published recommendations for managing this risk emphasize practical, coordinated measures. Pre-departure inspection to estimate biofouling levels, safe in-water cleaning that captures debris and residues, and forecasting likely first-call ports for advance notification are central. Rapid detection tools such as environmental DNA (eDNA) sampling and targeted visual surveys should be used by receiving ports to identify incursions early. Equally important are established communication channels and rapid alert systems among flag states, port authorities and national biosecurity agencies to prioritise actions where the risk is highest.
Both New Zealand and Australia maintain established marine biosecurity frameworks and have experience managing ships with biofouling risk, including responses led by Biosecurity New Zealand during the pandemic. While immediate arrivals from the Gulf may be limited, research indicates a meaningful number of potentially affected vessels could reach distant ports within a year. International coordination, timely inspections, containment-minded cleaning practices and early-use surveillance technologies will reduce the chance that these movements become an international biosecurity event.
