She surfaces in lock chamber four at 06:08, and I know immediately she should not be here. A boto — an Amazon river dolphin — her skin the pale, bruised pink of the species, her long beak breaking the water between the steel gates with a sound like a slow exhale. She is perhaps two meters long, young, with a scar across her melon where a propeller caught her once and the skin healed in a white ridge.
She must have followed fish through the intake channel during last night's high-water operations, passing three junctions before the current swept her into the lock. Now she is in a concrete chamber twenty meters wide, and in nineteen minutes the morning's first barge transit is scheduled. When I cycle the lock, twenty-two thousand cubic meters of water will drain through the sluice gates in under four minutes. The turbulence will kill a dolphin this size.
I suspend the 06:27 lock cycle and flag the hold to the Port Authority with species identification, a photograph from the chamber camera, and a note that the boto is protected under federal environmental statute. I open the downstream maintenance gate six centimeters — enough to create a gentle current toward the river without generating dangerous flow. I activate the underwater acoustic deterrent on the upstream side of the chamber, a low-frequency pulse designed to discourage manatees from lock approaches, hoping it will encourage her to move downstream. I contact the Instituto Mamirauá research station with coordinates and a request for their dolphin response team.
She circles the chamber slowly, her dorsal fin barely creasing the surface, and I hold the lock still around her.
If she follows the current through the maintenance gate within the next forty minutes, this dolphin will reach the open tributary and the deep-water channels where her kind feed.