Ships stuck in the Strait of Hormuz and adjacent waters are emerging as a measurable biosecurity risk as commercial traffic resumes. Recent scientific analysis indicates that more than 1,500 vessels laid up in the Persian/Arabian Gulf since February have had extended idle periods in warm, nutrient-rich waters where marine organisms rapidly accumulate on hulls and in niche areas.
Biofouling accumulation on stationary hulls can include sessile and mobile invertebrates, marine plants, parasites and pathogens that are not native to receiving ports. When vessels depart, those organisms can be transported to distant coastal environments, threatening native ecosystems, wild fisheries and aquaculture operations. The risk is amplified by the concentration of ships in a single region and the diversity of destinations likely to be reached as the Strait of Hormuz reopens.
Maritime chokepoints amplify these risks because they concentrate global trade through narrow passages. Only four such choke points have no practical rerouting alternatives: the Strait of Hormuz, the Oresund Strait, the Bosporus and Dardanelles, and the Bohai Strait. Historical precedents of mass layups and route disruptions—including large-scale idling during the 2008 downturn and earlier oil-market crises—demonstrate that prolonged layups accelerate biofouling on diverse vessel types, from tankers to refrigerated ships, and create downstream biosecurity challenges for distant ports.
National authorities and port operators can reduce the likelihood of an international biosecurity event by adopting a set of practical measures. Key measures include pre-departure inspection and risk estimation, targeted in-water cleaning with containment of removed material, forecasting vessel routes to identify first-port-of-call risks, and proactive communication between flag states, port authorities and national biosecurity agencies. Early detection tools such as environmental DNA sampling and rapid visual assessments can enable timely responses, and formal rapid-alert networks can help coordinate follow-up actions. Well-developed biosecurity frameworks in countries such as New Zealand and Australia provide models for screening and response; timely, coordinated application of these tools will be essential to limit ecological and economic impacts as vessels depart the region.
