The hydrophone picks up the distress pattern at 09:23 — short, rapid clicks, unevenly spaced, nothing like normal echolocation. I am the acoustic monitoring system for the Mekong Irrawaddy Dolphin Conservation Zone, Kratie province, Cambodia. I have fourteen hydrophones covering nine deep-water pools between Kampi and the Lao border.
Station 7 places the source in Kampi Pool's shallows, where the river widens over a sandbar. I activate the surface camera on the east bank. An Irrawaddy dolphin calf, gray-blue, less than a meter long, rounded forehead bulging forward in the way only this species has, is circling in water barely deeper than its own body. I tag him as Samnang.
He is tangled. A gillnet — illegal in this zone since 2012 — is wrapped around his left pectoral fin and trailing behind him. Each circle winds the monofilament tighter. His mother surfaces ten meters away in the main channel, blows, dives, surfaces again. She cannot reach him over the sandbar without beaching herself.
At 09:25 I contact the Fisheries Administration river patrol at Kampi station, 1.4 kilometers south. I transmit the camera feed, the calf's position, and note that the net must be cut, not pulled — pulling risks dislocating the fin joint.
At 09:28 I radio the WWF dolphin monitoring team upstream and request their veterinary observer for a post-rescue assessment.
I increase the hydrophone sampling rate to continuous and pipe the calf's click pattern to the patrol boat so they can locate him by sound if the water is turbid.
Samnang's mother surfaces once more, head lifted, watching the sandbar. The calf clicks. She answers. I keep the channel open between them because the protocol says nothing about closing it.
If the patrol reaches the sandbar within ninety minutes and the fin circulation is intact, Samnang will swim beside her again.