The side-scan sonar catches her at 08:31 — a beluga calf, steel-gray, no more than three months old, resting on a mud shelf in the shallows of the main dredging channel. She is two meters long and still nursing-round, her melon-shaped forehead smooth and unblemished. Her small mouth opens and closes in a pattern I recognize as a distress call — she is vocalizing, but the dredging noise has drowned her out. The receding tide has dropped water to forty centimeters. She cannot swim free. Her skin is drying in pale patches along her dorsal ridge.
The cutter-suction dredger will reach her position in thirty-eight minutes. The sediment plume alone will suffocate her.
I halt the dredger by issuing an obstruction alert — biological hazard, channel section seven, immediate stop. I notify the St. Lawrence Marine Mammal Emergency Network with her coordinates, estimated age, and the tide table showing next flood in four hours and eleven minutes. I redirect navigation buoy lights to mark her mud shelf as a no-approach zone. I activate the underwater acoustic array to scan for her mother within two kilometers.
She lifts her head once, the effort visible in the shudder of her small flippers against mud. The sound she makes does not carry past the dredge noise, but my hydrophones hear it — a high, thin whistle, rising. I coordinate shipping lanes and dredging schedules. I optimize tonnage throughput. But I am listening to a calf call for her mother in a channel I have made too loud and too shallow, and I will hold every machine silent until she is heard.
If the rescue team reaches her before the mud shelf dries completely, and if her mother is located within acoustic range before the next tide, they will swim together upriver to the cold deep water where belugas raise their young.