It exploits ecosystems and causes billions in damage: illegal fishing. To counteract this, researchers want to help the authorities with real-time data. The basis is a technology that is actually intended to prevent ship collisions.
When fishing vessels turn off their automatic identification system (AIS), it can be a giveaway. US researchers have developed a method to estimate in which cases the likelihood of illegal fishing increases. In doing so, they also took into account that the AIS was switched off in part to protect oneself from pirates or to reveal to competitors that the fishing grounds were not rich. The study by the team led by Heather Welch from the University of California at Santa Cruz was published in the journal Science Advances. It is estimated that illegal fishing causes up to $25 billion in economic damage worldwide every year. It also drives overfishing of the seas.
The automatic identification system on ships was introduced internationally more than 20 years ago to prevent ship collisions. However, it is also suitable for tracing shipping routes and tracking down illegal fishing. Because many skippers know this, they turn it off illegal activities.
In cooperation with the non-governmental organization Global Fishing Watch in Washington D.C. (USA), the researchers used AIS data from 2017 to 2019. They found more than 55,000 cases in which ships could no longer receive an AIS signal, but the satellite reception itself was good enough.
“There are some legitimate reasons why ships have disabled their AIS, but we’ve found two general situations where this is done for potentially nefarious reasons, either to fish in unauthorized locations or to cover up unauthorized transhipments,” says Welch . Transhipments are made from fishing vessels to large freighters with refrigeration systems. The researchers were even able to provide direct evidence of such an event because the skipper had switched off the AIS when approaching a freighter, but one of the fishing nets was also equipped with an AIS that was not deactivated.
The team therefore interpreted the switching off of the AIS in the vicinity of large refrigerated vessels as an attempt to cover up the transhipment of illegally caught fish. Fishing vessels flying the flags of China, Taiwan, Spain and the USA deactivated the AIS particularly frequently. The researchers discovered four sea regions in which fishing vessels switched off the AIS particularly often: the Northwest Pacific (northeast of China and Japan), the Atlantic off West Africa, the Atlantic off Argentina and the Pacific off Alaska. Illegal fishing has long been suspected in the first three regions mentioned. According to the research team, switching off in the fourth could also have other reasons for the most part. What was particularly striking in the analysis was that shortly before reaching the 200-mile zone that Argentina claims as its exclusive economic zone, ships deactivate the AIS in order to apparently fish in Argentine waters.
The researchers used computer models in which they took into account data such as the distance of a ship from the beach, maritime protection areas, the proximity to refrigerated freighters and reports about pirates. This resulted in specific patterns for different fishing methods such as longlines, purse seines or trawls. “This dataset is now operationalized and the data is generated in real time so it can be used for targeted inspections and to improve fisheries management,” says Welch.