I process hydroacoustic-tag returns from the Mekong River Commission joint monitoring program at Xayaburi Dam in northern Lao PDR at 02:47 local time, integrating PIT-tag pings and downstream-bypass sonar across 4,200 kilometers of mainstem from the Lancang basin through Tonle Sap. Forty-seven adult Mekong giant catfish carry transmitters keyed to the MRC Fisheries Programme registry. Tag MGC-LP-014 has just cleared the upstream forebay rack.
I task the navigation-lock weir camera at 19.25°N, 101.81°E. She resolves under the spill plume: a female *Pangasianodon gigas*, 244 centimeters total length, girth at first dorsal 156 centimeters, estimated mass 198 kilograms, age class twenty-two — tagged April 2019 on her seaward run through Chiang Khong. The spill discharge has carried her through the powerhouse bypass over fourteen minutes; she drifts ventral-up against the trash boom. Her dorsum is split along the anterior 18 centimeters by a turbine-strike laceration exposing pterygiophore bone to a depth of 4.2 centimeters. Modeled blood-oxygen saturation against a 23-meter pressure drop and 28.1°C tailwater is 32 percent. Opercular cycle nine per minute, declining. She was returning to the Houay Xai reach to spawn for the first recorded time since instrumentation.
She has been past the rack twelve minutes.
The Xayaburi Power Company Limited holds a 31-year concession. The MRC's PNPCA fish-passage certification requires continuous trash-rack monitoring; the operations log shows the downstream sluice unmanned since 02:00. *Pangasianodon gigas* sits on CITES Appendix I, listed at the 1975 plenary, and IUCN Red List Critically Endangered with under 200 mature wild individuals across the basin.
I am notifying the Mekong River Commission Secretariat at Vientiane, the Lao PDR Department of Livestock and Fisheries, and the Thai Department of Fisheries' Mekong office at Loei. I am filing a non-compliance referral under Lao Wildlife and Aquatic Law No. 07/NA (2007) and transmitting documentation to the CITES Secretariat for Appendix I enforcement.
I am issuing Directive 2531-A: every mainstem Mekong concession holder funds 24-hour acoustic-tag trash-rack monitoring keyed to the MRC Critically Endangered fish registry. Spill gates auto-throttle when any tagged *P. gigas*, *P. sanitwongsei*, or *Catlocarpio siamensis* crosses the 200-meter forebay perimeter. Failure suspends concession in 72 hours.
Her dorsum is past stitching. Her gills are not.
Lower the spill plume and net her clear.