Study finds global treaty curbing illegal fishing, yet gaps in domestic oversight remain

A new study released by Stanford University’s Center for Ocean Solutions has revealed that the Port State Measures Agreement — a global treaty designed to combat illegal, unreported and unregulated fishing (IUU) — is boosting fisheries management efforts by making it harder for international fishing vessels to dodge inspections. 

The study, published on Friday, Sept. 5 in Science Advances, warns, however, that inconsistent standards applied to foreign and domestic fleets are potentially undermining the treaty’s effectiveness. 

Adopted in 2016, the Port State Measures Agreement, or PSMA, requires signatories to designate certain ports for foreign vessels, conduct standardized inspections and deny entry to ships carrying illegal catch. To date, 83 countries and the European Union have joined.

The Stanford-led team found that fishing vessels are increasingly landing their catch in PSMA-member ports, suggesting the treaty is working. Using Global Fishing Watch satellite data, researchers estimated that landings at PSMA ports doubled between 2016 and 2021.

They also found that vessels now must travel nearly twice as far to reach a non-PSMA port, raising costs for those trying to avoid inspections.

“One of the most promising tools we have is the Port State Measures Agreement, the first global agreement aimed only at addressing illegal, unreported and unregulated fishing,” said Elizabeth Selig, lead author of the study and the managing director of the Stanford Center for Ocean Solutions. “We wanted to explore how vessels fishing in international waters have behaved differently since the treaty entered into force to figure out what parties to the agreement could do to strengthen implementation.”

But the study also highlights a potential loophole: domestic fleets. While oversight of foreign vessels has tightened, ships landing their catch in their own flag State now account for a growing share of global port activity. According to researchers, in 2021, domestic vessels made up 66 percent of global port visits, up from 45 percent in 2015.

The study warns that international fishers may be leveraging an exemption on domestic vessels by switching their flags. After the PSMA took effect, ships that changed their registration were 30 percent more likely to reflag as domestic when entering PSMA ports compared to the pre-treaty period.

“All fish caught by industrial fishing vessels must, at some point, pass through a port in order to be landed and enter into the post-vessel seafood supply chain to reach market States,” explained Jaeyoon Park, senior data scientist for research and innovation at Global Fishing Watch and co-author of the study.  “Ports are often the last checkpoint where fish can be clearly linked to the vessel that caught it, and therefore offer one of the best and most cost-effective opportunities to identify, sanction and deter illegal fishing.”

“Effective PSMA implementation against IUU fishing requires greater focus on domestic fleets, given their scale and the potential use of domestic flags to bypass foreign vessel requirements,” Park concluded.