The Strait of Hormuz remains effectively shut to international shipping as the double blow of Iranian and U.S. blockades leaves the key energy corridor largely dormant.

A tiny trickle of vessels, most with links to Iran, was observed in recent days. Traffic is generally steering clear after tensions in the waterway escalated last week as Iranian gunboats fired on ships, while U.S. forces seized two oil tankers.

Three Iran-linked ships exited the Persian Gulf through the strait on the morning of April 27, vessel-tracking data compiled by Bloomberg show. No incoming vessels were observed.

The Middle East war, now in its ninth week, has choked off vast supplies of crude and fuels to global markets. Oil is trading above $100 a barrel after efforts to resume peace talks stalled, leaving Hormuz almost impassable.

Ship Movements

Two bulk carriers and a liquefied petroleum gas tanker, all with ties to Tehran, departed the Gulf on April 27. That followed a quiet April 26, where commercial exits were limited to an Iran-linked fuel tanker and a bulk carrier, alongside two regional cargo ships. A fuel tanker with connections to China was seen entering the Gulf on April 26.

Most Iran-linked ships that exited in recent days didn’t sail past the Gulf of Oman. It isn’t yet clear whether those vessels were scheduled for regional stops or have been forced to wait out the U.S. navy blockade.

Vessels transiting Hormuz with active Automatic Identification System signals during the past day were confined to a narrow northern lane near the Iranian islands of Larak and Qeshm, a route approved by Tehran.

The U.S. blockade may encourage Iran-linked ships entering or leaving the Persian Gulf to switch off their signals to avoid detection, making it harder to get an accurate picture of traffic. That means transit figures may sometimes be revised higher when vessels reappear far away from the riskiest waters.

It was common, even before the U.S. imposed its latest restrictions, for Iran-linked ships to stop sending signals as they headed into Hormuz to exit the Persian Gulf. They generally didn’t enable them again until well into the Strait of Malacca in Southeast Asia, about 13 days’ sailing from Iran’s Kharg Island.

NOTES: 

Because vessels can move without transmitting their location until they’re well away from Hormuz, automated positioning signals were compiled over a large area covering the Gulf of Oman, the Arabian Sea and the Red Sea to detect those that may have departed or entered the Persian Gulf.

When potential transits are identified, signal histories are examined to determine whether the movement appears genuine or is the result of spoofing — where electronic interference can falsify the apparent position of a ship. 

Some transits may not have been detected, if vessels’ transponders haven’t been switched back on. Iran-linked oil tankers often steam from the Persian Gulf without broadcasting signals until they reach the Strait of Malacca, about 10 days after passing Fujairah in the UAE. Other ships may be adopting similar tactics, and won’t show up on tracking screens for many days.

This tracker will be published during heightened tensions involving Iran, and aims to capture traffic for all classes of commercial shipping.