The Tonle Sap Lake in Cambodia supports one of the most productive and biodiverse freshwater fisheries worldwide, sustaining livelihoods and food security for millions of people. However, essential data for sustainable fisheries management, such as fishing effort and harvest, is historically unreported and challenging to collect due to the lake’s vastness and remote location. This study demonstrates the applications of unmanned aircraft systems (drone) and satellite imagery, in combination with fish catch sampling, to quantify fishing effort and harvest by arrow traps in Siem Reap Province, Cambodia. Arrow traps are large (100-500m), indiscriminate fishing gear used extensively throughout the lake. Maps from satellite images revealed 859 and 1,123 traps operating in 2021 and 2022. This suggests a fourfold increase in fishing effort over the last twenty years. Spatial analysis of seasonal drone imagery collected in 2023 indicated changes in trap density over time, with the highest density (35 traps/sq.km) observed during the dry season and the lowest (1 trap/sq.km) in the wet season. The estimated harvest by these traps exceeds 2,900 tons/year, enough to support thirty thousand households and generate $720 thousand. This research provides the first report on fishing effort and harvest by arrow traps since the 1990s and presents innovative methods for monitoring traditional fishing gear in artisanal fisheries. These findings can guide efforts to combat unreported fishing globally and inform science-based regulations for sustainable fisheries management.

Authors:

Elizabeth Everest, Wonders of the Mekong, Ecology, Evolution and Conservation Biology Program, Department of Biology, College of Science, University of Nevada, Reno  (eeverest@unr.edu)

Tom Dilts, Natural Resources and Environmental Science Department, College of Science, University of Nevada Reno  (tdilts@unr.edu)

Sudeep Chandra, Director of the Ozmen Institute for Global Studies, Director of the Global Water Center, Department of Biology, College of Science, University of Nevada, Reno  (sudeep@unr.edu)

Peng Bun Ngor, Dean of the Faculty of Fisheries, Royal University of Agriculture, Cambodia  (pengbun.ngor@gmail.com)

Ken Nussear, Department of Geography, College of Science, University of Nevada Reno  (knussear@unr.edu)

Zeb Hogan, Director of the Wonders of the Mekong project, Global Water Center, Department of Biology, College of Science, University of Nevada, Reno  (zhogan@unr.edu)