But then the tracks had begun to vary, becoming increasingly erratic; this was due, Piya believed, to changes in the composition of the waters of the Sundarbans. As sea levels rose, and the flow of fresh water diminished, salt water had begun to intrude deeper upstream, making certain stretches too saline for the dolphins. They had started to avoid some of the waterways they had frequented before; they had also, slowly, begun to venture further and further upriver, into populated, heavily fished areas.
