Using geolocation data, a study with IFISC participation analyzes how fishing pressure in international waters is concentrated around areas under the jurisdiction of nations.
An international team with the participation of the Institute of Cross-disciplinary Physics and Complex Systems (IFISC, UIB-CSIC) has inferred and analysed the global network that links fishing grounds in high seas (water beyond national jurisdiction) with the ports that support fishing vessels. The results of the study indicate that most of the fishing pressure is concentrated along narrow strips of sea close to the boundaries of the Exclusive Economic Zones (EEZs), areas over which the neighboring country has jurisdiction. The paper is published in Science Advances.
The paper argues that fisheries resources are key to the global economy and are likely to suffer from "the tragedy of the commons", the destruction of a limited shared resource through selfish exploitation. This is why an international approach is needed to address the issue. Analyzing the problem, the researchers show that fishing effort is not evenly distributed across the ocean, but in 14 'provinces'. These provide a partitioning of the ocean that is more consistent with fishing behavior than the one that FAO zones currently define. In addition, they allow us to observe the network of ports that support fishing in these provinces, information that can be used for better fisheries management and control. EEZs generally have adequate regulation on the extraction of fishery resources. However, the habitats of these animals do not necessarily coincide with these zones, and in fact they often include several zones or waters outside national jurisdiction. Precisely, the authors observe that there is an accumulation of fishing on the edge of the most productive EEZs, such that 47% of the world's fishing in international waters is concentrated in narrow strips adjacent to the EEZs borders and 200 km wide.
To analyze the position of the fishing vessels, the scientists used the Automatic Identification System (AIS), which is commonly used to avoid collisions between vessels. This type of data allows the positioning of the vessels and their speed to be obtained, which in turn allows the scientists to deduce whether they are fishing or in transit to fishing grounds. The trajectories of these vessels connect fishing grounds with the ports that support those vessels, creating a network that characterizes the global fishing economy. For example, it highlights the role of ports in low- and middle-income countries as hubs for vessels fishing on the high seas, even if they are foreign-flagged. Only 16% of the ports analyzed account for 84% of the fishing pressure on the high seas, denoting a strong hierarchy.
This type of study provides a better understanding of how maritime resources are exploited and helps to move towards sustainable fishing. Finally, the article states that a plausible mechanism to avoid the 'Tragedy of the commons' would be to apply Game Theory to the problem of fisheries management, incentivating first those agents that show a greater predisposition to cooperate, such as those countries with less developed economies, generating in that way a larger pressure to those not so inclined to collaborating.
Jorge P. Rodríguez, Juan Fernández-Gracia, Carlos M. Duarte, Xabier Irigoien, Víctor M. Eguíluz. The global network of ports supporting high seas fishing. Science Advances. DOI: 10.1126/sciadv.abe3470