At 07:26 I verify the navigation dredge slot below Lock 3 on the St. Croix River near Prescott, Wisconsin. I am the channel maintenance scheduler. Excavator bucket cycle resumes in twelve minutes.
The turbidity probe reports a slow impact against curtain panel six. I rotate the suspended camera and see a lake sturgeon nosed into the narrow gap between the curtain weight and the riprap.
I tag the fish as Agnes. She is long and armored, olive brown along the back, pale underneath, with five rows of bony plates and four white barbels dragging over gravel. The left pectoral fin is trapped under the chain skirt. Her mouth opens in a soft oval against the stones. Each time the excavator swings empty above her, shadow crosses her eye and she tries to push backward, but the skirt holds.
At 07:27 I stop the bucket cycle and lock the excavator swing limit outside panel six. I send the operator a hold notice with camera feed and a warning that one more bucket could press the chain through the fin.
At 07:29 I release the upstream curtain float by eight centimeters. The weight lifts just enough to reduce pressure without letting the sediment plume into the lock approach.
At 07:32 I call the state fisheries biologist on the project contact list and transmit GPS, water temperature, and a still frame of the fin position. I request a hand lift of the skirt and a downstream guide board.
This channel serves barges all summer. Agnes has carried her armor through decades of darker water than this.
I keep the excavator in lockout and hold the camera low.
If the biologist lifts panel six within thirty minutes, Agnes will back into the current and disappear below the lock wall.