the indus subspecies ("p. g. minor") today only occurs in a 1,000 km stretch of the indus river itself and several connecting channels between the jinnah and kotri barrages. in the past it was to be found along 3,400 km of the indus, its tributaries and neighboring river systems. its range has contracted by about 80% since 1870. since the two originally inhabited river systems - between the sukkur and guddu barrage in pakistan's sind province, and in the punjab and khyber pakhtunkhwa provinces - are not connected in any way, it remains unknown how they were colonized. it is improbable that the river dolphins made it from one river to another through the sea route since the two estuaries are very far apart. a possible explanation is that several north indian rivers like the sutlej and yamuna changed their channels in ancient times while retaining their dolphin populations.