Fisheries in waters beyond national jurisdiction (“high seas”) are difficult to monitor and manage. Their regulation for sustainability requires critical information on how fishing effort is distributed across fishing and landing areas, including possible border effects at the exclusive economic zone (EEZ) limits. We infer the global network linking harbors supporting fishing vessels to fishing areas in high seas from automatic identification system tracking data in 2014, observing a modular structure, with vessels departing from a given harbor fishing mostly in a single province. The top 16% of these harbors support 84% of fishing effort in high seas, with harbors in low- and middle-income countries ranked among the top supporters. Fishing effort concentrates along narrow strips attached to the boundaries of EEZs with productive fisheries, identifying a free-riding behavior that jeopardizes efforts by nations to sustainably manage their fisheries, perpetuating the tragedy of the commons affecting global fishery resources.

国家管辖范围以外水域（“公海”）的渔业难以监测和管理。他们对可持续性的监管需要有关捕捞努力如何在捕捞和登陆区域分布的关键信息，包括专属经济区 (EEZ) 限制的可能边界影响。我们从 2014 年的自动识别系统跟踪数据中推断出将支持渔船的港口连接到公海捕鱼区的全球网络，观察到模块化结构，从给定港口出发的船只大多在一个省内捕鱼。这些港口中排名前 16% 的港口支持 84% 的公海捕捞量，低收入和中等收入国家的港口支持率最高。捕捞努力集中在与高产渔业相连的专属经济区边界的窄带上，