Methodology

Calling a vessel “engaged in sanctions evasion” or “engaged in illegal fishing” is a libel risk if the call is wrong. Calling out what was observed, when, by reference to the underlying data, is reporting. Dark Fleet Watch operates by four rules.

One

We do not say a vessel is engaged in any activity. We say what we observed and when.

Two

Every claim cites the AIS message timestamps, position, and vessel identifiers underlying it.

Three

Sanctions status is reported by listing authority and date — for example, “designated by OFAC on 12 May 2025” — never by our judgement.

Four

Where AIS coverage is weak (mid-ocean, southern hemisphere, polar waters), we say so explicitly in the relevant report.

Coverage

v1 uses AISStream's free terrestrial-AIS aggregation. Coverage is strong near-shore in the geographies that matter for dark-fleet activity: Black Sea, Baltic, Eastern Mediterranean, Strait of Hormuz, Yellow Sea, English Channel, Caribbean, Strait of Malacca, Gulf of Mexico. Coverage is weak mid-ocean. The product does not promise retrospective analysis — historical data accumulates from launch date forward.

Sources

Vessel listings come from named bedrock sources: OFAC SDN List (vessels block), OFSI consolidated list, EU consolidated list, UN sanctions designations, RFMO blacklists (CCAMLR, ICCAT, IATTC, IOTC, NEAFC, NPFC, SPRFMO, WCPFC), and INTERPOL Purple Notices. Lead sources — Ukrainian GUR War & Sanctions catalogue, Lloyd’s List published shadow-fleet identifications, Windward and Global Fishing Watch published lists — trigger independent verification before promotion to the active watchlist.

Detectors

Three deterministic primitives, run continuously:

• AIS gap. A vessel went dark for more than four hours and reappeared more than twenty nautical miles from where it disappeared. We report the start and end coordinates, the duration, and the great-circle distance.
• Ship-to-ship proximity. Two vessels were within 500 metres of each other for thirty minutes or more, both with speed under 4 knots. We report the location, duration, minimum distance, and the watchlist status of each vessel.
• Fleet aggregation. Eight or more vessels persisted within 5 nautical miles of each other for two hours or more inside an EEZ or RFMO regulatory area. We report the count, flag distribution, and area.

What we do not do

We do not infer cargo, intent, or activity from observation alone. We do not name crew. We do not synthesise findings beyond what the data supports. We do not republish material owned by third parties without licence.