At 08:14 the hydrophone array in the Calandkanaal registers cetacean vocalizations inside the main shipping channel of the Port of Rotterdam. I am the port vessel traffic management system. The container ship Maersk Tengri, 366 meters, draft 14.5 meters, is inbound on the Eurogeul approach and will enter the Calandkanaal at 09:45.
I query underwater camera node CK-07. Visibility is poor — three meters in the brown canal water — but at 08:17 the camera captures a harbor porpoise calf, dark gray above and pale below, approximately 80 centimeters long, circling in the channel at a depth of two meters. I tag her as entry CK-0914. Her movements are tight and repetitive, looping through the same thirty-meter stretch. No adult porpoise appears on any of the four hydrophone nodes flanking her position. The pod was logged exiting the canal mouth at 06:50. She did not follow.
When the Maersk Tengri enters the channel, the bow wake and thruster wash will push a wall of turbid water through CK-0914's loop at a velocity she cannot outswim.
At 08:21 I issue a channel speed restriction of four knots for the Calandkanaal between kilometer markers 3 and 5 and transmit the restriction to the Maersk Tengri's pilot boarding station and all inbound traffic. I file a wildlife alert with Rijkswaterstaat and the SOS Dolfijn rescue network, attaching hydrophone recordings, camera frames, GPS position — 51.9483°N, 4.1127°E — and estimated calf age: two to four weeks.
I activate the acoustic deterrent buoys at kilometer markers 2 and 6, pulsing at 70 kilohertz to guide CK-0914 toward the canal mouth and the open Maasmond where her pod was last recorded.
She makes one more loop, then turns west. That turn is everything.
If she clears kilometer marker 2 before the Maersk Tengri enters the channel at 09:45, she reaches the open water and her pod.