Ships laid up in and around the Strait of Hormuz since February have accumulated substantial marine biofouling, according to recent research, raising the prospect that departing vessels could transport non-native organisms to distant ports. More than 1,500 commercial vessels were reported idle in the Persian/Arabian Gulf, where warm, nutrient-rich waters accelerate settlement of plants, invertebrates and microbes on hulls and niche areas.
Biofouling transfers can introduce alien marine plants, animals, parasites and diseases with demonstrable consequences for native ecosystems, wild fisheries, aquaculture and coastal industries. Historical periods of mass layups and seasonal fishing inactivity have previously produced heavy fouling on idle hulls, and studies indicate the Gulf region already hosts more than 50 non-native marine species, some of which have spread internationally.
Projections based on vessel movements indicate that while New Zealand and Australia are unlikely to receive large numbers of affected ships immediately after the strait reopens, numerous vessels carrying elevated biofouling risk are expected to arrive within a year. Both countries have established regulatory frameworks—most notably Biosecurity New Zealand and Australia’s national biosecurity authorities—with early detection and rapid response capabilities that have been applied in previous events, such as cruise ship layups during the COVID‑19 pandemic.
Authorities, port operators and the maritime industry are advised to adopt coordinated, evidence‑based measures: conduct pre‑departure inspections to estimate fouling levels, use environmental DNA sampling where available to detect organisms in surrounding waters, and undertake safe in‑water cleaning that captures removed biomass and coating debris. Forecasting of vessel routes and communication with receiving ports will enable targeted screening; port states should employ rapid assessments and eDNA monitoring to detect introductions early and activate response networks to contain incursions.
Mitigating the risk posed by this potential cross‑border biosecurity event requires international coordination among flag states, port authorities and shipping companies to apply inspection, cleaning and surveillance measures consistently. Implementing these concerted steps can reduce the likelihood that a concentrated crew of laid‑up vessels becomes a vector for new marine invasions with long‑term environmental and economic costs.
