Ships laid up in the Strait of Hormuz region present a measurable biosecurity threat as the waterway reopens. Recent research documents that more than 1,500 commercial vessels anchored in the Persian/Arabian Gulf since February have had prolonged stationary periods during which hulls and niche areas can accumulate marine plants, animals, parasites and pathogens. If those organisms are transported to new ports, they may establish populations that harm native ecosystems, wild fisheries, aquaculture and coastal industries.
The Strait of Hormuz is one of only a handful of global choke points that lack viable alternative routes, and shipping disruptions there can lead to concentrated vessel layups. Historical precedents include mass idling after the 2008 financial crisis and tanker layups during the 1970s oil shock. Tropical and subtropical waters accelerate biofouling growth, increasing the probability that idle ships leave with significant biological material attached.
Australia and New Zealand face particular exposure because the Persian/Arabian Gulf hosts more than 50 documented non‑native marine species and several Gulf natives have become global invaders. Modelling and vessel movement studies indicate many affected ships will transit to diverse destinations within a year. Both countries have established biosecurity regulations and operational capabilities — for example, Biosecurity New Zealand implemented screening and remedial measures for cruise ships during the COVID‑19 layups — but short‑term arrivals remain a management challenge.
Practical mitigations are available and can be coordinated internationally. Prior to departure, vessels should be inspected to assess visible fouling and, where feasible, subject to environmental DNA sampling to characterize biological risk. Where safe containment can be ensured, in‑water cleaning that captures removed material is preferable to translocation. Forecasting first‑port destinations and rapid communication with port authorities enable targeted checks. Receiving states should maintain early‑detection capacity, low‑cost rapid assessments and agreed rapid‑response pathways, supported by real‑time alerting networks for biosecurity events.
Managing this potential marine biosecurity “super‑spreader” event requires coordinated action between flag states, port authorities and international agencies. Timely inspections, transparent information sharing and investment in detection and response will reduce the likelihood that vessel layups in the Gulf translate into long‑term ecological and economic impacts elsewhere.
