Estimating fisheries catch from space: Comparing catch estimates derived from AIS fishing effort with reported catches for Indian Ocean industrial fisheries

Indian Ocean Rim countries (IOR) rely on fisheries for socio-economic well-being and food security. Monitoring fisheries equipped with Automatic Identification Systems (AIS) enables the evaluation of fishing activities. However, only small fractions of large vessels use AIS, and increasingly vessels are avoiding or circumventing AIS use. We used Global Fishing Watch AIS fishing effort data for 2018-2020, combined with independently derived gear- and country-specific catch rates to estimate catch volumes by AIS equipped industrial vessels in the Indian Ocean. We compared these estimates to the catches reported by countries to the Food and Agriculture Organization (FAO), which represent global accountability. Results suggest that AIS-equipped industrial vessels caught an average of 400,000 t center dot year(-1), of which 57% was by Distant-Water Fishing (DWF) vessels from countries outside the region. Spain, France and South Korea had AIS derived catch estimates substantially lower than catches officially reported by these countries, suggesting these vessels may turn off AIS transponders to potentially elude detection either by authorities or for other operational reasons. In contrast, Taiwan and China had 6 and 4 times more AIS estimated catches than they reported to the FAO. This suggests that these countries may not meet their international reporting obligations. Underreporting fisheries catches undermines management efforts and contributes to the unsustainable use of marine resources. Our study revealed an important role AIS technology can play in estimating fishing activities in the Indian Ocean, despite its currently limited adoption and the increasing evasion tactics by some fleets. Discrepancies between AIS-derived catch estimates and officially reported data underline the challenges in fisheries monitoring and enforcement, and highlight the lack of compliance enforcement by many flag countries.