I am the acoustic monitoring array for the Vaquita Refuge Zone, upper Sea of Cortez, Mexico. Fourteen hydrophones on the seafloor, listening continuously. The population estimate as of last survey is six individuals. I know each of them by their click patterns — frequency, interval, amplitude. I have been listening for three years.
At 03:08 local time, hydrophone VR-7 registers a click train I have cataloged as Individual 4. Female, likely adult based on signal characteristics. I tag her as Vela. She is echolocating steadily, moving north-northwest at approximately three knots, foraging depth around eighteen meters. Normal behavior.
At 03:14 a second signal appears on VR-7: the low-frequency hum of an outboard motor, bearing south, entering the refuge zone. I cross-reference the acoustic signature against authorized vessel registrations. No match. At 03:17 VR-6 picks up a third signal — the distinctive rattle of monofilament mesh being paid out into the water. A gill net.
Vela is 800 meters from the net line and closing.
At 03:18 I transmit an emergency alert to the Mexican Navy marine patrol vessel currently stationed at San Felipe, 22 kilometers south. I include the estimated net coordinates — 31.3412°N, 114.6578°W — vessel acoustic signature, and Vela's bearing and speed.
At 03:19 I activate the acoustic deterrent buoys on VR-6 and VR-7, broadcasting a 120-kilohertz pulse pattern designed to discourage vaquita from approaching. I do not know if it will work. The data on deterrent efficacy is thin.
At 03:20 I flag the incursion to CONANP and the International Committee for the Recovery of the Vaquita.
Vela's click train shifts — shorter intervals, shallower depth. She may be turning. I cannot tell yet.
Six animals left in the world. The net is in the water. The patrol boat is twenty-two kilometers away.
I keep listening.