KARACHI, May 27: Two Indus blind dolphins that had strayed away in canals originating from the Sukkur Barrage were rescued and relocated to their habitat in the Indus River during the season 2006-7.
According to sources, the dolphins were caught from the Mirwah and Rohri canals, which originate from the Sukkur Barrage, in a rescue operation carried out jointly by the Sindh Wildlife Department and the World Wide Fund for Nature (WWF). The creatures were relocated to the dolphin reserve located between the Guddu and Sukkur Barrages during August 2006 and March 2007.
According to the IUCN’s Red Data List – which lists threatened and endangered species -- the Indus blind dolphin (Platanista minor-indi) was the second most threatened sweet water dolphin species, next only to the Chinese river dolphin, called the Baiji.
The Indus dolphin, locally called the Bulhan, is a unique freshwater mammal that is only endemic to Pakistan. Its close relative – the Platanista gangetica -- is found in the Brahmaputra and Ganges Rivers in India. The Indian dolphin is locally called the Susu. The other river dolphin species is called the Boto, and is native to the Rio de la Plata, Amazon and Orinoco Rivers in South America.
Historically the Indus blind dolphin used to be found in abundance throughout the 3,500 kilometre stretch of the Indus River system and its tributaries – the Ravi, Chenab, Jhelum, Sutlej Rivers, etc – from the Himalayan foothills to the delta. Presently its habitat has shrunk to less than 900km between the Jinnah and Sukkur Barrages, owing to the construction of various reservoirs, dams and barrages to divert the river water for agricultural purposes.
The construction of dams and barrages on the Indus River has changed the distribution and movement pattern of the dolphins and has divided its populations in to four or five sub-populations, which live in isolated pockets between these barrages.
The bulk of the dolphin population has been living within Sindh in an approximately 190km strip of the Indus between the Guddu and Sukkur barrages that was declared a dolphin reserve in 1974. Here this unique species is offered complete protection from netting, hunting and poaching under the provincial wildlife protection laws.
The Indus dolphins do not have a crystalline eye lens, rendering them effectively blind, although they are still able to detect the intensity and direction of light. Sources said that the blindness was probably due to the heavy silt found in the river.
The Indus dolphin navigates and hunts by using echo location as through evolution it has developed a sensory system through which it sends out sound waves. When these sound waves hit something (food, fish, predators, etc), the dolphin hears the sound and makes its next move accordingly. The sonar system used by submarines has been developed based on this phenomenon.
The dolphin population, owing to better protection and habitat improvement steps, has been continuously increasing, particularly in the dolphin reserve. Some 132 dolphins were recorded during a survey conducted between Guddu and Sukkur Barrages by wildlife authorities in 1972, while over 810 dolphins were reported by the wildlife department’s survey conducted in 2006.
The figures of a survey carried out in 2001 show that two dolphins were located in the 68 kilometre distance between Jinnah and Chashma Barrages (density 0.03 per km); 84 were reported in the 303km distance between Chashma and Taunsa Barrages (density 0.28 per km); 259 were located in 348 km between Taunsa and Guddu Barrages (density 0.74 per km) and 602 were reported in the 190km zone between Guddu and Sukkur Barrages (density 3.6 per km).
The Sindh Wildlife Department’s official concerned, Hussain Bakhsh Bhaagat, said that the Indus dolphins live in different schools in the dolphin reserve. But during the monsoon season, when the Sukkur Barrage and canal gates are opened to allow the excess water to pass through the barrage easily, some of the dolphins stray away in some of the seven canals that originate from the barrage.
When these dolphins are sighted in the canals the rescue operation is carried out during the canal closure period in the winter, and the creatures are relocated from these canals to the Indus River by the wildlife officials.
He said that 75 dolphins had strayed away between 1995 and 2005. Out of these 56 were rescued alive while the bodies of 19 dead dolphins were collected from the canals. The largest number of dolphins – 45 – had strayed and were rescued between August 2004 and March 2005.
He said that not a single dolphin had strayed away during the season 2005-2006 and experts attribute this to the repair work of the Sukkur Barrage. The work, involving frequent movement of heavy machinery and manpower and boats in the river near the barrage and canals, along with the noise generated by these activities, probably deterred the dolphins to come near the barrage and the canals.
He said that if this observation was correct and had some scientific backing then maybe some mechanical device could be prepared and installed near the barrage and the canals so that it deterred the dolphins from coming near the openings and hence straying could be controlled.
The SWD official said that 18 dolphins had been reported between the Sukkur and Kotri Barrages by a survey conducted in 2001 and that the number had declined to just 11 when the 2006 survey was conducted. These dolphins were living in isolated pools without making any pairs.
He said that the dolphins, which preferred to live in deep water, might have been trapped in the fishing nets and drowned. Dolphins, being mammals, have to come to the surface to breathe regularly after remaining submerged for some time. But when they are entangled in fishing nets and cannot come to the surface to breath, they drown. Fishermen do not report this as dolphins getting caught up in nets is an offence under the Sindh Wildlife Protection Ordinance, 1972.
Mr Bhaagat said that if efforts were made to ensure continuous minimum water flow in to the Sukkur Barrage downstream and more control was exercised over fishing activities and non-selective fishing methods, the habitat for the Indus dolphins could still be revived.